If it was my boat, I'd keep what's there. It's dry and solid, you can skin it with more glass and even add another core layer which would significantly enhance the structure when you install the pod extension. Remember, you started with a project boat. If you wanted a completely new boat, you'd have started with a mold. :)
I'd say if you're going to take the core out of that transom, just cut the whole back out. Yeah it means rebuilding most of the transom from nothing. But it also means you're done with the tear down in a day, and the heavy lifting part is construction, rather than grinding and tear down.
I've been watching you for a while now. And the one thing I noticed is you DON'T take shortcuts, nor do you put out shoddy work. Whatever you do will turn out better than factory. I for one, what you to keep it and get that boat out on Superior with your family. :)
If the transom core is in good shape, keep it. However, I would enlarge all of the current drilled holes and fill with epoxy and redrill. This will help to ensure that any future water intrusion around the bolts for the outboard motor platform is protected from the wood core.
I used a lot of encapsulated exterior grade Fir plywood when I refit my sailboat. We tore it all apart for recycling last year and after twenty-seven year's on the ocean I didn't have a single area that water got into. My point being, and as you already know, properly done plywood is an excellent product for use on boats.
I've so been there on cutting where I shouldn't, not on a boat, though, on a piano soundboard (I'm a piano technician). Recovering from that actually gave me some skills that provided me a decent living over the years, but it sure as hell didn't seem like that at the time!! In terms of your poll, due what your patrons vote for. I'd be one if I could afford it... I've learned a lot, and really appreciate your instructive videos!
Build it out & roll with it. In 35-40yrs you won’t be worried about boats at that time! Go get it done & enjoy it, summer time is around the corner. While we are all still here, go enjoy as you much as possible. Stay safe & keep the good videos rolling! 🍻⛵️
I understand wanting to have the peace of mind that it has been replaced with the coosa, but with the amount of work it will take to rip out a perfectly good transom, I think you should leave it. Take the time to make sure it’s sealed up perfectly and move on.
When you are building an awesome boat, and coming this far, why stop at 90% awesome? Also, from an educational standpoint, showing viewers how to overcome a pain in the butt job, and do it in totality, and finish with an unquestionably structurally sound job is something great in itself. As for everyone saying they want to see it on the water immediately, there are tons of other channels to watch with boats on the water. I found this channel because I was learning how to work on my boat.
This would be my preferred approach, as it removes the need to also strip the solid plywood core, allows you build a brand new transom and even potentially removes the need of a transom bracket!
@@AdrianoCisternino yep, that was my reasoning too. And one more thing, I really think it will be faster, inboard versus outboard needs a longer length.
Hi Andy, I voted to keep the plywood, but I do have a caveat to that vote. Rip that funky wood out of the old key holes. At that point you can make a couple of judicious cuts and assess how well the plywood is bonded around the key holes. If it is solid, then fill in the key holes and beef the rest of the transom up. If there is delamination, well you know what you have to do.
I think u should do the full coosa transom , for a few reasons. #1 more content for ur channel .I mean ur channel really help me with my 17ft boston super sport now it's perfect . #2 u wont have to ever redo it #3 it will be even stronger I mean the ocean is unpredictable and with ur family involved. Safety is no 1 priority. By the way love them bertram my dream boat.
As far as the transom per se, I doubt it matters structurally which method you choose. I'm confident you can do either correctly or make it look fantastic. Consider doing whatever is less time consuming. Now that the dead and live live loads (especially thrust) you've added to the transom by using outboards will be adequately supported by the transom, the concern is to ensure that the these loads will be transmitted to the stringer system and hull bottom/sides adequately to prevent over stressing the stringer/hull frame (racking and flexing). Great project Andy. Love the series.
You've gotten this far with removal of virtually the entirely of the reinforcement area. If you continue on to the actual area they reinforced, you'll eliminate the uncertainty of questions about that area. You'll be starting a new chapter for the reliability of the entire project, because You have addressed the area, compleatly. The engines are large and lots to stress to the transom area is transferred from them to this area, best to know what you have with No surprises. Great work Andy!👍🏻
I for one would like to see you fix the transom as is. Your work is stellar, and I believe it would be more realistic for us viewers to see you repair from the solid " leftovers" you have now. Love your work and channel !
Couldn't find the link to the poll. Everyone is going to say RIP out all wood and go with coosa .But seriously will the boat still be on the water 40 years now? Its solid wood ,you obviously know what you are doing, leave well enough alone and strengthen the top. Love your videos keep up the good work.
Andy, great job. You are a true pro. With transoms being a big problem with a lot of boats. I would like to see it stripped down to the plywood and replaced properly. A lot of viewers would benefit from the correct way to do their boats correct. Please show how to check for moisture before you tear in to the job👍
Keep it and do your thing, it’s fine, like you said, it’s gonna last. I have no doubt whatsoever it will be perfect and strong enough to hold those monsters!!
Andy, don't spend all that time and headache ripping out the plywood. Since the plywood is dry then it will be fine like you say for 20-30 years, it makes no sense to remove it. I'd say just thicken it up with the new foam boards, enlarge the holes and fill them with epoxy and re-drill them to the original size so the plywood stays fully sealed. It will be more than strong enough. Love the attention you give to these projects, really great workmanship !
thank you for the non virus related content. also... Mas on sail life had the same decision to make regarding his rotted stringers on athena. he decided to simply reinforce in place with enough material to make the rotted cores a non-issue because quite simply it was the easiest path to a workable solution. i learn something valuable and new from each of your videos and though i would dearly love to see the process of removal and reinforcement, perhaps the best lesson learned here is, "if it aint broke don't fix it."
Pez Pengy I think Mads messed up by just glassing over the rotten beams. If just adding a few more layers of glass made it as strong as glass laminated over wood don’t you think the original designer would have just made the whole thing out of a few more layers of glass to start with. There is no way that Mads way is stronger than original glass over wood plank . He may regret it later. I hope not though.
@@mwatkins2464 Mads Athena stringer lay up was engineered to the hull weight, there is no way it is weaker than the original in original condition which relied on the wood core (which decomposed) as part of the stringer strength. Go back and watch how many layers it took before you say "few more layers" again so you transfer the info accurately.
Why would the original designer add that much more glass? It's waiste of time and money. Also, how accurate durability calculations were in 1985? If any analysis was made in the beginning. I think Mads had a finite element analysis made to assess his options with the stringers. His only possible problem with the rotten wood is the added smell to the boat.
@@mwatkins2464 In a beam most of the strength is in the outside. The middle is just there to keep the outside in the right place. An I beam is a good example. The two big flanges take the load and the middle web just keeps the flanges in the right place. Mads added a lot of glass on the outside so those beams are probably much stronger than the origainal setup. It wasn't done that way in the factory because it is difficult to glass over air to create a hollow structure. Also wood is a lot cheaper than glass.
After watching the video, reading the replies and incorporating my experience as limited as it may be. Your there, hands on ... If the core is absolutely solid and your confident you can seal the finished product -if anyone can, you can- just go ahead a build up. But if anything in your being questions that rebuild, give in to your ocd and rip it all out. I feel certain"YOU" can do a great job either way you go but in the end ... Will you have confidence in the transom work to take out family and friends? Personally, if the core is solid and I know my work and effort will result in a better structure that will last 20 or 30 years minimum. Build it up!!! You already have it down to the original Hull and if that is good then why go through the added time and expense. Find out the specs for the Armstrong bracket and meet or exceed it. I look forward to seeing which way you go and the final product. As always, great work on everything to do.
Hi, why not use fr4 instead of the coosa? Can you go with a thinner fr4 vs coosa? Is there a large cost difference and what are the pros and cons of the choice of material properties on the stern? Great video. It seems cutting into the bottom was the right thing to do all things considered.
Hi Andy what is interesting to me is seeing how well or not so well new material has bonded to the old or original material. I think this is a lesson in being suspicious of all repairs or modifications. I have watched your videos covering the bond quantity between epoxy and polyester but this really demonstrates the importance of getting that right. I know these flat panels don't take much sheer strain but somewhat surprised how easily they are separating.
Andy, I’ve been watching your videos for a long time and you are one of the best on “how to” instructor videos I’ve seen on UA-cam. My question is that why not go further in conducting an experiment to put your skills to the test. Why not discard the outboard bracket and run stringers through the transom and make an integral outboard bracket? Personally, if I had the time, which a lot of folks might have during this epidemic I’d rather do something that would last for a long time. You have the shop, the materials to do it and with some imagination it can be done.?
Andy I’m on the fence on what I would do, if the boat is going to sit in the water during the boating season 24/7 where it has more of a chance to develop leaks, I might consider replacing the plywood, if the boat is going to be trailered to and from the lake, I would probably leave it, just my thoughts 👍😁
Hey Andy, I would drill a few test holes around where the bolts go though the transom about 3 or 4 " from the hull check for rot near the bolts. That may give you better idea what mitt be happening with the wood in the transom. If you find it to be dry, fill in the top and glass over the inside of the transom leaving the hull ID plate open. I mitt even clean that off so it is easy to read if that is possible. Tech tips from Yachtsmen's tool box .
You are wise to be cautious about tearing apart more than necessary. Why use a core on top of what is there. Would it not be stronger to just lay up glass? I understand the need to redo the transom openings for the stern drives.
I'm currently replacing the transom on my 2000 striper seaswirl in which you gave me advice via email and your fiberglass resin guide (thanks again)..being that its an older boat I wanted to keep costs down so I bonded marine ply to existing glass with thickend epoxy and finished the rest of the glass with pe resin. I came to this conclusion using the repair workflow chart on your resin guide.. according to that you should use laminating pe or ve resin for all repair work. I like charts like that it makes decisions like this easier. Hope this helps
You already know the core is good. I would level it out the way you were originally thinking then Coosa board all the way up and across. I would worry more about the "oops" than anything else. Tying that back into the transom is going to be the weak link so I would tie that in first before doing the transom. You're already in there anyway so why not do a little overkill and do two layers of coosa board and make it to the thickness you know will be safe, then you would also have more strength at that joint repair. Just my two cents. I enjoy your videos, and you gave me the confidence to do a pretty aggressive project on a 235 Glastron. Keep up the good work and good luck on this project.
Andy the Hull was built for inboards not twin outboards on a bracket. If you just had the outer skin right now, how would you build the inside of the transom up to your desired thickness? 3" of coosa and a thick well laid up inner skin with offset tabbing or various thicknesses of plywood and glass, and some pine for the keyholes? I'm sure you could find out what Bertram would recommend or get the opinion of a naval architect or engineer. Maybe not a situation for "well it lasted this long it should be good." Lake Superior is cold and deep even in the summer.
I would recommend working with what you have already but rather than huge layups increase the overall structure by bonding coosa stiffness into an appropriate structural grill and then tab and glass it all in. Similar to the bilge in a modern sailing yacht - know what I mean?
A tip for removing the Armstrong bracket; support the bracket with your hoist then use a long piece of 80lb mono or braided fishing line, tie some sticks around the ends and wrap it around the joint and saw trough the 5200 like butter. When you remount the bracket leave a new rip cord for the next guy before you use your 5200 or boat works similar. Looks Good, Bill W
i dont know if you have fixed the transom problem, but i think i would extend the frame you are sitting on to be bolted on to the upper row of bolts from the transom, i cant see if there is also a metal frame in the bottom of the old engine well, but givven that that is where the torque originally was transferred that should be able to take the power..
Happy Sunday Andy how you doing this is big knucklehead down here in Miami Florida I would say keep the existing and build off of it two reasons one you already done a full transom rebuild video and this will give us a different look of how to address transom issues and second since you have already determined that everything under there's pretty much good then it makes no sense of burning through material in order to replace something that's not broken at least that's my two cents brother hope you and your family are well and healthy and I look forward to seeing your next video thanks
I’d keep the existing and build from there. With your experience in the proper bonding of materials you should have no problems. Are you going to tie the transom into the bottom of the boat as well similar to what the previous owner did but better?
I removed all the coring in my transom, but it was an easy decision since the original was badly patched by a previous owner and largely mulch in many areas. If yours is sound, I'd be tempted to just build upon what is already there and solid.
I vote leave the core since it is good. Build up around it like you said then put a large piece over the whole thing to increase thickness. Is there any place for aluminum bracing to help strengthen the whole thing???
Hey Andy! I think you should keep the original core and build off of that. Removing that is gonna be a pain and in my opinion unnecessary. It will last long if it doesn’t get wet. Maybe build up the top of the transom with coosa and fiberglass over the whole thing a couple of times and make it smooth. That would be good content with a lot of information showing build up and fairing. Whatever you do I’ll be here on Sunday morning! 👍
I was taught “if it ain’t broke don’t fix it”. You have said that plywood is stronger than coosa. If you leave it you know you will do whatever is necessary to ensure it is water tight. The time saved can be put towards other repairs and as others have said, you will be on the water sooner rather than later.
"Given that it's a weak area" l would ask Bertram if they have an approved schedule? I've been with you for awhile now, and this is your own boat so l know you won't be taking any short cuts. Has this modification been done before, as with any vehicle in a fluid, move the engines will have an effect on buoyancy, and center of gravity. Have any calculations been made? I suspect that the outboard mounting bracket is calculated to offset the this, might be a good idea to double check? Love your channel it would make a good video to show the weight and balance much and center of gravity or vertical center of buoyancy. I put a much heavier engine on a homebuilt (successfully) to avoid drag inducing ballast in the tail moved the engine back about 6" to compensate. 👍👍👍👍 I expect you've already got those bases covered. For the amount of work already done, l'd put a router on a 18" X 12" clear Pespex/Lexan base and rout out as much of the ply as possible before resorting to hand tools (l suppose a Festool multicut with the depth stop or a shop rigged depth stop would be helpful) and replace with non-rotting water permeable ply. Just on the grounds l wouldn't want to be revisiting it again after all the strengthening has gone over it. 😭😭😭 Excellent work and l am sure however you tackle the troublesome transom will be a well thought out and practical solution. 👍👍👍👍👍👍👍👍👍 It it was a drunken sailor l'd put him in the scuppers with a hose pipe on him🤭 Addendum Say the original engine was 500lbs and the center of that mass 30" inboard of the transom, and a 25' boat is level in the water. (25 X 12 - 30) X 500 = 135,000 lb inches for equilibrium (floats level) (25 X 12 + 30) X 800 = 264,000 lbs inches Or Close on nearly double. Very approx equivalent to putting a 1000 lbs heaver inboard, yeap not sure how much effect that would have, interesting stuff 🤔👍🤣 (check my Math could be wrong guessed wait of original engine and arm length ) probably not a biggy l thinking its like 4 big blokes moving from midships to standing on the transom.
Never saw a transom that didn't have water around the drain plug. I would have to put at least a larger layer of wood over the outdrive holes so all the joints don't fall on the same spot. How does the outside glass look around those holes?
Keep what’s there , build off of that . Be extra vigilant on sealing it up when you reinstall all the hardware. Coat every hole that has to go through the transom liberally with an epoxy or some other waterproofing that will soak in thoroughly inside the holes . 👍👍😊
After many years of doing different projects on cars, boats and buildings (i moved my own house to it's present location) there comes a point where it is easier to start from the beginning than to try to go over someones else's work. Replace the whole transom because you will regret not doing it. Referring to my own house every time that i make a repair or modify it to suit my needs, I end up doing more work than required. For example the wiring in the house is mostly 14 gauge wire, when you increase the load you have to rewire the area with 12 or even 10 gauge wire. To accomplish this you have to open up the wall to remove the old wire and replace it with new. Another time one of the floor joist had cracked at a large knot at the stairway opening you had to remove the stairs to replace it. It would have be easier to build the house from the ground up rather than constantly rebuilding it.
My question to you is gonna be!!! Whats gonna give YOU the GREATEST peace of mind! what is gonna be the strongest, as others have said if it aint broke dont fix it! but if this is gonna be for you and your family, then you have to do what you believe is gonna be best. I would build up the low area and then finish the whole area with the coosa like you described. Take care and be safe.
BTW the leaking bolt is a red herring, there was no water leaking OUT Between the Armstrong mount and the transom. Only has to be water tight on that joint, that bolt is INSIDE the water tight compartment. Andy your good 👍👍👍👍👍👍👍
Have you ever thought about using a router flattening jig, as woodworkers do when flattening slabs for table tops and so? That could ease your work when adding layers of coosa. Fill up the low spots. Flatten the surface and then add one large panel piece instead of creating a puzzle. You might wanna invest in a large vacuum though, to catch all the dust that the router creates. I've never tried it my self, but the thought seems worthwhile thinking about. My guess about the piece removed by misstake. It will ease your work because the transom became a whole lot flatter surface to work on. And the saved time and effort on the transom will worth more than the time and effort lost.
I work for a boatyard and have installed many armstrong brackets, and even have one on my own boat. Standard transom thickness is about 2". Two 3/4 sheets of plywood or coosa laminated together, and outside skin of 3/16 to 1/4 and an inside skin of about an 1/8. In good condition that will support a bracket and twin 130's no problem. The Bertram 25 was initially designed for inboards only and only has a small section of traditionally cored transom. That bump-out area. Should be two layers of 3/4 plywood in there. The rest of the transom is solid glass but thin, as you discovered. I'd leave the existing plywood core, redo the keyholes, and laminate two layers of 3/4 coosa over the entire inside of the transom, using filler or oddball pieces to bring all the levels up. I would then also build some coosa knees to tie the transom to the top of every stringer. On my 1979 23 seacraft I installed an armstrong bracket on, I did three knees. One to each of the tops of the large box stringers, and another to the center stringer. I would also remove the bracket from the transom and grind off the bottom paint and re-bed the bracket to the hull NOT to the top coat of the existing bottom paint, which is how it looks. With the bracket off you could also dig out the transom core from around every bracket bolt hole and fill with thickened epoxy and re-drill. Then the core would be truly sealed and you would have nice solid chunks of epoxy in the transom to tighten the bolts to. Just my .02 cents USD. Loving your videos, as I do a lot of systems and structrual work, but am just getting into the refinishing aspect of boat work. Learning a lot from you about gelcoat and paintwork. Keep up the good work!
I vote for no replacement however I would extend the upper taped area further up the transom by removing that bulged out area above the tape. Without extending it up further I believe that you will still have a hinged point just below the bulge and will be subject to future breakage. Yes I know you will be putting additional larger pieces over that but deep inside there will be a weak point below the bulge.
I didn't see an active link to the poll, maybe try it out on the community tab? Either way, my vote is to leave it to your great grandchildren's greater ingenuity and access to new technologies to address it in the future restoration 40 years from now. It might be novel and quaint to see actual wood at that point. Think of their smiles! Plus Lase-rbeaming it off with a robot will probably be as common as using a tape measures by then.
Careful of project creep, if it ain't broke don't fix it. The whole "while I'm here I should...." results in a project you never get to enjoy, scab it all up to the same level then add a solid panel on top of that.
Hi Andy: Think about the worse case scenario. The two outboard on the transom. Heading into heavy seas with all the torque of those outboard motors. Think of something happened to that transom; because you didn’t take it apart to see if was made strong enough for the two outboards.
All stress will now be at port and starboard side under gunnel. You dont need to go all the way acrossed to sides and lock it in.building up transom is great . but if the sides cant hold stress also its pulling on corners and sides of boat
If its as good and dry as you think it probably is. Skin it and add some supports overlapping those weak spots. One option is to build a bracket support to transfer the load onto the old engine mounts so to say that way you might eliminate any twisting when throttling up. If in doubt just over do it :) keep up the great work 💪
I take it that you thought it needed to be redone because it looked like a hack job? Rip it all out so you never have second thoughts that you are doing a re-hack job.
Xylene / Xylol is common solvent used in cleaners and is at times even used as thinner of paints (when wanting it to take longer to dry vs typical paint thinners that has quicker flash point). 5200 on the other hand uses Glycol (Diethylene Glycol Monoethyl Ether), likely to help it bond with polyester resins and polyurethanes since glycol is typically used in those as well. So in theory a Glycol solvent would work best at breaking down 5200 ... but it would also do the same to the polyester resin which you are not wanting to do. Acetone and MEK (Methyl Ethyl Ketone) as I am sure you know are used in marine industry to remove 5200, and they do work well. However, specific products like Marine Formula Debond, Anti-Bond and similar product Goo Gone has tested to work easier allegedly. I never have tried them, just use MEK which works ok. And MEK is easier to get and likely cheaper then those other special products, which again may work better but MEK works good enough than to go to all that hassle of finding and paying more. But this makes me wonder if one my old personal fav solvents of Lacquer Thinner would work as well, since it is basically just MEK, Toluene and Naptha. Strong stuff though, so only use it when its needed.
Keep the core if something happens to it later on it would be due to neglect or misuse, neither is your problem. You might also consider wrapping the new material around both sides of the boat as well for additional strength perhaps 6'' or more up the sides, think of it as the difference between the ease of bending a flat shaped bar verses an L shaped bar.
Do you have, or could you make, a video on the different materials you use and the tools as well. What they all do and how they're used? Kind of a fiberglass 101. You're the best fiberglass teacher on UA-cam
After rebuilding the whole boat, I would not leave the old transom in there. The water meter may not pick up moisture because it’s been inside your shop for several years. Tear it out and replace with something you know is solid.
Build off what is there! Double glass the sides of Coosa and pre drill some small fill holes. After each Coosa board is tabbed in, squirt some filler in the holes starting low and going up. (micro balloons/spheres & resin?) 😃
Rip out out drive fillers. If transom wood OK leave it in place and glass in really good fit non rot replacement. Level up transom as you add another 1 - 2 inches of thickness. Ensure all bolt holes are fully sealed with resin before sealing bolts in place. Glad it's you doing it and not me.
Why the dewaxer worked is not because of the xylene necessarily, but the fact the surface of the old glass was not properly prepared for the G10 and 5200 that was added on top. The wax on the surface of the glass then was broken down by the xylene and BAMM! No more bond and it peels off fairly easily. I have used 5200 and wiped the top off it down with xylene and not had it deteriorate.
I voted to rip it out just because I’d love to see how you do it. But I believe either way it will outlast any of us because I know you’ll make sure it’s better than Bertram could ever had made it.
No chance like the present one to replace. Much much easier now to go all the way. That said, a looooot more time and effort whereas you could just reinforce what is there and be 99% confident that it will be fine.
I heard ya start to quote Ave at 13.55... nice. I would think sanding, layering another core and glassing it all in wouldn't be a bad thing. If the core isn't damaged, let it be. It was made right and sealed properly.
Replace the whole thing, cons...more work and more materials, pros...you are the kind of guy that likes everything done the right way, coosa over plywood will be hammering in your head as long as you own the boat, coosa is stronger than plywood and weights less, plus it doesn't matter if by any chance you have water intrusion through the screw holes, another pro is that it will make more episodes for your UA-cam channel and that's how you are making money now, plus there are a lot of us that really enjoy your videos and the super quality work you do, all that while helping others, like me.
I think you answered yourself when you drilled the test hole and only had 1/4 to 3/8 of glass and no core. Stern Drives and outboards are two different animals when it comes to transfer of thrust to hull. Most of the sd’s thrust is low and partially thru front engine mounts. Outboards have a tendency to pull from the top and push low. Now you change the thrust vector by moving that power 1 to 2 feet back and you’ve made a pretty big lever that wants to tear the top loose from sides of the hull. Your only option is to check with the bracket mfg and get with them on how much that 3” spec must be above in relation to top mount bolts. I would also try to tie the top of the transom to side hull. Easier now than to have a failure and a “ Go Back”.
I'm not educated enough to have an answer that will help you. But as a fan I'll support your decision either way. That being said, I'd love to see this thing in the water this year.
I would use 1/4 coosa then layer of fiberglass till it is all level and then continue till you get the thickness you want. For the bolt holes, core out a 2 to 3" hole fill with a coosa plug and thickened epoxy to seal the plywood.
I'd really need to know more about the engines. Do the outboard need to push against the transom? Or does most of the force go into the engine and engine beds? What does the manufacturer recommend?
There are so many inconsistencies in the current transom layup. I feel that an all new core and layup would not only be stronger but much lighter. Best of luck with your decision.
If it was my boat, I'd keep what's there. It's dry and solid, you can skin it with more glass and even add another core layer which would significantly enhance the structure when you install the pod extension. Remember, you started with a project boat. If you wanted a completely new boat, you'd have started with a mold. :)
Open the keys holes for further examination. If everything is fine then repair key holes and add crisscross pattern of acoosa to build transom.
Does Coosa have "grain?" Would he end up with better strength going crosswise than he would with overlapping laminations?
I know little to nothing so bare with me, I do believe Coosa board is bidirectional.
I'd say if you're going to take the core out of that transom, just cut the whole back out. Yeah it means rebuilding most of the transom from nothing. But it also means you're done with the tear down in a day, and the heavy lifting part is construction, rather than grinding and tear down.
I've been watching you for a while now. And the one thing I noticed is you DON'T take shortcuts, nor do you put out shoddy work. Whatever you do will turn out better than factory. I for one, what you to keep it and get that boat out on Superior with your family. :)
If the transom core is in good shape, keep it. However, I would enlarge all of the current drilled holes and fill with epoxy and redrill. This will help to ensure that any future water intrusion around the bolts for the outboard motor platform is protected from the wood core.
I used a lot of encapsulated exterior grade Fir plywood when I refit my sailboat. We tore it all apart for recycling last year and after twenty-seven year's on the ocean I didn't have a single area that water got into. My point being, and as you already know, properly done plywood is an excellent product for use on boats.
I've so been there on cutting where I shouldn't, not on a boat, though, on a piano soundboard (I'm a piano technician). Recovering from that actually gave me some skills that provided me a decent living over the years, but it sure as hell didn't seem like that at the time!! In terms of your poll, due what your patrons vote for. I'd be one if I could afford it... I've learned a lot, and really appreciate your instructive videos!
May just be me, but if the current setup is dry and solid I’d reinforce it an be done with it.
Build it out & roll with it. In 35-40yrs you won’t be worried about boats at that time! Go get it done & enjoy it, summer time is around the corner. While we are all still here, go enjoy as you much as possible. Stay safe & keep the good videos rolling! 🍻⛵️
I understand wanting to have the peace of mind that it has been replaced with the coosa, but with the amount of work it will take to rip out a perfectly good transom, I think you should leave it. Take the time to make sure it’s sealed up perfectly and move on.
When you are building an awesome boat, and coming this far, why stop at 90% awesome? Also, from an educational standpoint, showing viewers how to overcome a pain in the butt job, and do it in totality, and finish with an unquestionably structurally sound job is something great in itself. As for everyone saying they want to see it on the water immediately, there are tons of other channels to watch with boats on the water. I found this channel because I was learning how to work on my boat.
Right, bold suggestion, lengthen the boat and incorporate the mounting for the engines.
This would be my preferred approach, as it removes the need to also strip the solid plywood core, allows you build a brand new transom and even potentially removes the need of a transom bracket!
@@AdrianoCisternino yep, that was my reasoning too. And one more thing, I really think it will be faster, inboard versus outboard needs a longer length.
Hi Andy, I voted to keep the plywood, but I do have a caveat to that vote. Rip that funky wood out of the old key holes. At that point you can make a couple of judicious cuts and assess how well the plywood is bonded around the key holes. If it is solid, then fill in the key holes and beef the rest of the transom up. If there is delamination, well you know what you have to do.
I think u should do the full coosa transom , for a few reasons. #1 more content for ur channel .I mean ur channel really help me with my 17ft boston super sport now it's perfect . #2 u wont have to ever redo it #3 it will be even stronger I mean the ocean is unpredictable and with ur family involved. Safety is no 1 priority. By the way love them bertram my dream boat.
As far as the transom per se, I doubt it matters structurally which method you choose. I'm confident you can do either correctly or make it look fantastic. Consider doing whatever is less time consuming. Now that the dead and live live loads (especially thrust) you've added to the transom by using outboards will be adequately supported by the transom, the concern is to ensure that the these loads will be transmitted to the stringer system and hull bottom/sides adequately to prevent over stressing the stringer/hull frame (racking and flexing). Great project Andy. Love the series.
I think if you're gonna fill the key holes with glass you should just redo the whole thing and make it all a solid piece of coosa.
You've gotten this far with removal of virtually the entirely of the reinforcement area.
If you continue on to the actual area they reinforced, you'll eliminate the uncertainty of questions about that area.
You'll be starting a new chapter for the reliability of the entire project, because You have addressed the area, compleatly.
The engines are large and lots to stress to the transom area is transferred from them to this area, best to know what you have with No surprises.
Great work Andy!👍🏻
I for one would like to see you fix the transom as is. Your work is stellar, and I believe it would be more realistic for us viewers to see you repair from the solid " leftovers" you have now. Love your work and channel !
Couldn't find the link to the poll. Everyone is going to say RIP out all wood and go with coosa .But seriously will the boat still be on the water 40 years now? Its solid wood ,you obviously know what you are doing, leave well enough alone and strengthen the top. Love your videos keep up the good work.
Andy, great job. You are a true pro. With transoms being a big problem with a lot of boats. I would like to see it stripped down to the plywood and replaced properly. A lot of viewers would benefit from the correct way to do their boats correct. Please show how to check for moisture before you tear in to the job👍
Getting ready to do the transom on my 26 CC and binge watching all your videos. Appreciate the effort taken to film and starting your channel.
Keep it and do your thing, it’s fine, like you said, it’s gonna last. I have no doubt whatsoever it will be perfect and strong enough to hold those monsters!!
Andy, don't spend all that time and headache ripping out the plywood. Since the plywood is dry then it will be fine like you say for 20-30 years, it makes no sense to remove it. I'd say just thicken it up with the new foam boards, enlarge the holes and fill them with epoxy and re-drill them to the original size so the plywood stays fully sealed. It will be more than strong enough. Love the attention you give to these projects, really great workmanship !
I'd like to see you get out on the water this year.
Mars Rover it’s illegal right now in south Florida.
thank you for the non virus related content. also...
Mas on sail life had the same decision to make regarding his rotted stringers on athena. he decided to simply reinforce in place with enough material to make the rotted cores a non-issue because quite simply it was the easiest path to a workable solution. i learn something valuable and new from each of your videos and though i would dearly love to see the process of removal and reinforcement, perhaps the best lesson learned here is, "if it aint broke don't fix it."
Pez Pengy I think Mads messed up by just glassing over the rotten beams. If just adding a few more layers of glass made it as strong as glass laminated over wood don’t you think the original designer would have just made the whole thing out of a few more layers of glass to start with. There is no way that Mads way is stronger than original glass over wood plank . He may regret it later. I hope not though.
@@mwatkins2464 Mads Athena stringer lay up was engineered to the hull weight, there is no way it is weaker than the original in original condition which relied on the wood core (which decomposed) as part of the stringer strength. Go back and watch how many layers it took before you say "few more layers" again so you transfer the info accurately.
Why would the original designer add that much more glass? It's waiste of time and money. Also, how accurate durability calculations were in 1985? If any analysis was made in the beginning.
I think Mads had a finite element analysis made to assess his options with the stringers. His only possible problem with the rotten wood is the added smell to the boat.
@@mwatkins2464 In a beam most of the strength is in the outside. The middle is just there to keep the outside in the right place. An I beam is a good example. The two big flanges take the load and the middle web just keeps the flanges in the right place. Mads added a lot of glass on the outside so those beams are probably much stronger than the origainal setup. It wasn't done that way in the factory because it is difficult to glass over air to create a hollow structure. Also wood is a lot cheaper than glass.
After watching the video, reading the replies and incorporating my experience as limited as it may be. Your there, hands on ... If the core is absolutely solid and your confident you can seal the finished product -if anyone can, you can- just go ahead a build up. But if anything in your being questions that rebuild, give in to your ocd and rip it all out.
I feel certain"YOU" can do a great job either way you go but in the end ... Will you have confidence in the transom work to take out family and friends?
Personally, if the core is solid and I know my work and effort will result in a better structure that will last 20 or 30 years minimum. Build it up!!! You already have it down to the original Hull and if that is good then why go through the added time and expense. Find out the specs for the Armstrong bracket and meet or exceed it.
I look forward to seeing which way you go and the final product. As always, great work on everything to do.
Andy, Keep what ya have if it's good and build that bad boy up. I did a small transom this summer and it was one heck of a job.
Hi, why not use fr4 instead of the coosa? Can you go with a thinner fr4 vs coosa? Is there a large cost difference and what are the pros and cons of the choice of material properties on the stern? Great video. It seems cutting into the bottom was the right thing to do all things considered.
Hi Andy what is interesting to me is seeing how well or not so well new material has bonded to the old or original material. I think this is a lesson in being suspicious of all repairs or modifications. I have watched your videos covering the bond quantity between epoxy and polyester but this really demonstrates the importance of getting that right. I know these flat panels don't take much sheer strain but somewhat surprised how easily they are separating.
You have invested so much time on this Boat to make it like new. Change the whole thing!
Andy, I’ve been watching your videos for a long time and you are one of the best on “how to” instructor videos I’ve seen on UA-cam. My question is that why not go further in conducting an experiment to put your skills to the test. Why not discard the outboard bracket and run stringers through the transom and make an integral outboard bracket? Personally, if I had the time, which a lot of folks might have during this epidemic I’d rather do something that would last for a long time. You have the shop, the materials to do it and with some imagination it can be done.?
Andy I’m on the fence on what I would do, if the boat is going to sit in the water during the boating season 24/7 where it has more of a chance to develop leaks, I might consider replacing the plywood, if the boat is going to be trailered to and from the lake, I would probably leave it, just my thoughts 👍😁
would love to see how to replace a wood transom with coosa and if the wood goes bad, then you'll need to remove the coosa and the wood
noli novio look up born again boating on UA-cam he’s done a refit with coosa
Hey Andy, I would drill a few test holes around where the bolts go though the transom about 3 or 4 " from the hull check for rot near the bolts. That may give you better idea what mitt be happening with the wood in the transom. If you find it to be dry, fill in the top and glass over the inside of the transom leaving the hull ID plate open. I mitt even clean that off so it is easy to read if that is possible. Tech tips from Yachtsmen's tool box .
You are wise to be cautious about tearing apart more than necessary. Why use a core on top of what is there. Would it not be stronger to just lay up glass? I understand the need to redo the transom openings for the stern drives.
I'm currently replacing the transom on my 2000 striper seaswirl in which you gave me advice via email and your fiberglass resin guide (thanks again)..being that its an older boat I wanted to keep costs down so I bonded marine ply to existing glass with thickend epoxy and finished the rest of the glass with pe resin. I came to this conclusion using the repair workflow chart on your resin guide.. according to that you should use laminating pe or ve resin for all repair work. I like charts like that it makes decisions like this easier. Hope this helps
You already know the core is good. I would level it out the way you were originally thinking then Coosa board all the way up and across. I would worry more about the "oops" than anything else. Tying that back into the transom is going to be the weak link so I would tie that in first before doing the transom. You're already in there anyway so why not do a little overkill and do two layers of coosa board and make it to the thickness you know will be safe, then you would also have more strength at that joint repair. Just my two cents. I enjoy your videos, and you gave me the confidence to do a pretty aggressive project on a 235 Glastron. Keep up the good work and good luck on this project.
Andy the Hull was built for inboards not twin outboards on a bracket. If you just had the outer skin right now, how would you build the inside of the transom up to your desired thickness? 3" of coosa and a thick well laid up inner skin with offset tabbing or various thicknesses of plywood and glass, and some pine for the keyholes? I'm sure you could find out what Bertram would recommend or get the opinion of a naval architect or engineer. Maybe not a situation for "well it lasted this long it should be good." Lake Superior is cold and deep even in the summer.
I would recommend working with what you have already but rather than huge layups increase the overall structure by bonding coosa stiffness into an appropriate structural grill and then tab and glass it all in. Similar to the bilge in a modern sailing yacht - know what I mean?
A tip for removing the Armstrong bracket; support the bracket with your hoist then use a long piece of 80lb mono or braided fishing line, tie some sticks around the ends and wrap it around the joint and saw trough the 5200 like butter. When you remount the bracket leave a new rip cord for the next guy before you use your 5200 or boat works similar. Looks Good, Bill W
i dont know if you have fixed the transom problem, but i think i would extend the frame you are sitting on to be bolted on to the upper row of bolts from the transom, i cant see if there is also a metal frame in the bottom of the old engine well, but givven that that is where the torque originally was transferred that should be able to take the power..
Happy Sunday Andy how you doing this is big knucklehead down here in Miami Florida I would say keep the existing and build off of it two reasons one you already done a full transom rebuild video and this will give us a different look of how to address transom issues and second since you have already determined that everything under there's pretty much good then it makes no sense of burning through material in order to replace something that's not broken at least that's my two cents brother hope you and your family are well and healthy and I look forward to seeing your next video thanks
I’d keep the existing and build from there. With your experience in the proper bonding of materials you should have no problems. Are you going to tie the transom into the bottom of the boat as well similar to what the previous owner did but better?
I removed all the coring in my transom, but it was an easy decision since the original was badly patched by a previous owner and largely mulch in many areas. If yours is sound, I'd be tempted to just build upon what is already there and solid.
I vote leave the core since it is good. Build up around it like you said then put a large piece over the whole thing to increase thickness. Is there any place for aluminum bracing to help strengthen the whole thing???
Hey Andy! I think you should keep the original core and build off of that. Removing that is gonna be a pain and in my opinion unnecessary. It will last long if it doesn’t get wet. Maybe build up the top of the transom with coosa and fiberglass over the whole thing a couple of times and make it smooth. That would be good content with a lot of information showing build up and fairing. Whatever you do I’ll be here on Sunday morning! 👍
Andy I've seen some stuff on UA-cam where you create a cavity at pour it in. you should look into it . I forget what it's called but it pours.
I was taught “if it ain’t broke don’t fix it”. You have said that plywood is stronger than coosa. If you leave it you know you will do whatever is necessary to ensure it is water tight. The time saved can be put towards other repairs and as others have said, you will be on the water sooner rather than later.
Definitely keep it, it seems to add work for little benefit.
"Given that it's a weak area" l would ask Bertram if they have an approved schedule?
I've been with you for awhile now, and this is your own boat so l know you won't be taking any short cuts.
Has this modification been done before, as with any vehicle in a fluid, move the engines will have an effect on buoyancy, and center of gravity. Have any calculations been made? I suspect that the outboard mounting bracket is calculated to offset the this, might be a good idea to double check? Love your channel it would make a good video to show the weight and balance much and center of gravity or vertical center of buoyancy. I put a much heavier engine on a homebuilt (successfully) to avoid drag inducing ballast in the tail moved the engine back about 6" to compensate. 👍👍👍👍 I expect you've already got those bases covered.
For the amount of work already done, l'd put a router on a 18" X 12" clear Pespex/Lexan base and rout out as much of the ply as possible before resorting to hand tools (l suppose a Festool multicut with the depth stop or a shop rigged depth stop would be helpful) and replace with non-rotting water permeable ply. Just on the grounds l wouldn't want to be revisiting it again after all the strengthening has gone over it. 😭😭😭
Excellent work and l am sure however you tackle the troublesome transom will be a well thought out and practical solution.
👍👍👍👍👍👍👍👍👍 It it was a drunken sailor l'd put him in the scuppers with a hose pipe on him🤭
Addendum
Say the original engine was 500lbs and the center of that mass 30" inboard of the transom, and a 25' boat is level in the water.
(25 X 12 - 30) X 500 = 135,000 lb inches for equilibrium (floats level)
(25 X 12 + 30) X 800 = 264,000 lbs inches
Or Close on nearly double. Very approx equivalent to putting a 1000 lbs heaver inboard, yeap not sure how much effect that would have, interesting stuff 🤔👍🤣 (check my Math could be wrong guessed wait of original engine and arm length ) probably not a biggy l thinking its like 4 big blokes moving from midships to standing on the transom.
Never saw a transom that didn't have water around the drain plug.
I would have to put at least a larger layer of wood over the outdrive holes so all the joints don't fall on the same spot. How does the outside glass look around those holes?
Keep what’s there , build off of that . Be extra vigilant on sealing it up when you reinstall all the hardware. Coat every hole that has to go through the transom liberally with an epoxy or some other waterproofing that will soak in thoroughly inside the holes . 👍👍😊
Drill fill drill
Good work. Scary how bodgers can wreck a boat. Make it like new, those big outboards will really add stress it wasn't meant to take.
After many years of doing different projects on cars, boats and buildings (i moved my own house to it's present location) there comes a point where it is easier to start from the beginning than to try to go over someones else's work.
Replace the whole transom because you will regret not doing it.
Referring to my own house every time that i make a repair or modify it to suit my needs, I end up doing more work than required. For example the wiring in the house is mostly 14 gauge wire, when you increase the load you have to rewire the area with 12 or even 10 gauge wire. To accomplish this you have to open up the wall to remove the old wire and replace it with new. Another time one of the floor joist had cracked at a large knot at the stairway opening you had to remove the stairs to replace it.
It would have be easier to build the house from the ground up rather than constantly rebuilding it.
A lot depends on what your hanging on the back . if 1000 HP + or 4 outboards do not skimp anything .out and replace with largest sheet sizes possible
My question to you is gonna be!!! Whats gonna give YOU the GREATEST peace of mind! what is gonna be the strongest, as others have said if it aint broke dont fix it! but if this is gonna be for you and your family, then you have to do what you believe is gonna be best. I would build up the low area and then finish the whole area with the coosa like you described. Take care and be safe.
BTW the leaking bolt is a red herring, there was no water leaking OUT Between the Armstrong mount and the transom.
Only has to be water tight on that joint, that bolt is INSIDE the water tight compartment. Andy your good 👍👍👍👍👍👍👍
Have you ever thought about using a router flattening jig, as woodworkers do when flattening slabs for table tops and so? That could ease your work when adding layers of coosa. Fill up the low spots. Flatten the surface and then add one large panel piece instead of creating a puzzle. You might wanna invest in a large vacuum though, to catch all the dust that the router creates.
I've never tried it my self, but the thought seems worthwhile thinking about.
My guess about the piece removed by misstake. It will ease your work because the transom became a whole lot flatter surface to work on. And the saved time and effort on the transom will worth more than the time and effort lost.
I work for a boatyard and have installed many armstrong brackets, and even have one on my own boat.
Standard transom thickness is about 2". Two 3/4 sheets of plywood or coosa laminated together, and outside skin of 3/16 to 1/4 and an inside skin of about an 1/8. In good condition that will support a bracket and twin 130's no problem.
The Bertram 25 was initially designed for inboards only and only has a small section of traditionally cored transom. That bump-out area. Should be two layers of 3/4 plywood in there. The rest of the transom is solid glass but thin, as you discovered.
I'd leave the existing plywood core, redo the keyholes, and laminate two layers of 3/4 coosa over the entire inside of the transom, using filler or oddball pieces to bring all the levels up. I would then also build some coosa knees to tie the transom to the top of every stringer. On my 1979 23 seacraft I installed an armstrong bracket on, I did three knees. One to each of the tops of the large box stringers, and another to the center stringer.
I would also remove the bracket from the transom and grind off the bottom paint and re-bed the bracket to the hull NOT to the top coat of the existing bottom paint, which is how it looks.
With the bracket off you could also dig out the transom core from around every bracket bolt hole and fill with thickened epoxy and re-drill. Then the core would be truly sealed and you would have nice solid chunks of epoxy in the transom to tighten the bolts to.
Just my .02 cents USD.
Loving your videos, as I do a lot of systems and structrual work, but am just getting into the refinishing aspect of boat work. Learning a lot from you about gelcoat and paintwork. Keep up the good work!
I'd make sure to put in three knees going to the stringers. Center one to the keel.
I vote for no replacement however I would extend the upper taped area further up the transom by removing that bulged out area above the tape. Without extending it up further I believe that you will still have a hinged point just below the bulge and will be subject to future breakage. Yes I know you will be putting additional larger pieces over that but deep inside there will be a weak point below the bulge.
I didn't see an active link to the poll, maybe try it out on the community tab? Either way, my vote is to leave it to your great grandchildren's greater ingenuity and access to new technologies to address it in the future restoration 40 years from now. It might be novel and quaint to see actual wood at that point. Think of their smiles! Plus Lase-rbeaming it off with a robot will probably be as common as using a tape measures by then.
Go all the way up for future equipment mounting! Just build off it.
Careful of project creep, if it ain't broke don't fix it. The whole "while I'm here I should...." results in a project you never get to enjoy, scab it all up to the same level then add a solid panel on top of that.
I'd replace it. That way to know 100% for sure its solid and stays that way.
Keep it and build off it! Most boat owners would follow that course me thinks!
Hi Andy:
Think about the worse case scenario. The two outboard on the transom. Heading into heavy seas with all the torque of those outboard motors. Think of something happened to that transom; because you didn’t take it apart to see if was made strong enough for the two outboards.
All stress will now be at port and starboard side under gunnel. You dont need to go all the way acrossed to sides and lock it in.building up transom is great . but if the sides cant hold stress also its pulling on corners and sides of boat
Don't fix what isn't broke. I'm sure you'll seal it properly and it will last forever. Beef it up and keep up the good work! Love your videos.
If its as good and dry as you think it probably is. Skin it and add some supports overlapping those weak spots. One option is to build a bracket support to transfer the load onto the old engine mounts so to say that way you might eliminate any twisting when throttling up. If in doubt just over do it :) keep up the great work 💪
I take it that you thought it needed to be redone because it looked like a hack job? Rip it all out so you never have second thoughts that you are doing a re-hack job.
Xylene / Xylol is common solvent used in cleaners and is at times even used as thinner of paints (when wanting it to take longer to dry vs typical paint thinners that has quicker flash point). 5200 on the other hand uses Glycol (Diethylene Glycol Monoethyl Ether), likely to help it bond with polyester resins and polyurethanes since glycol is typically used in those as well. So in theory a Glycol solvent would work best at breaking down 5200 ... but it would also do the same to the polyester resin which you are not wanting to do. Acetone and MEK (Methyl Ethyl Ketone) as I am sure you know are used in marine industry to remove 5200, and they do work well. However, specific products like Marine Formula Debond, Anti-Bond and similar product Goo Gone has tested to work easier allegedly. I never have tried them, just use MEK which works ok. And MEK is easier to get and likely cheaper then those other special products, which again may work better but MEK works good enough than to go to all that hassle of finding and paying more. But this makes me wonder if one my old personal fav solvents of Lacquer Thinner would work as well, since it is basically just MEK, Toluene and Naptha. Strong stuff though, so only use it when its needed.
Keep the core if something happens to it later on it would be due to neglect or misuse, neither is your problem. You might also consider wrapping the new material around both sides of the boat as well for additional strength perhaps 6'' or more up the sides, think of it as the difference between the ease of bending a flat shaped bar verses an L shaped bar.
Do you have, or could you make, a video on the different materials you use and the tools as well. What they all do and how they're used? Kind of a fiberglass 101. You're the best fiberglass teacher on UA-cam
After rebuilding the whole boat, I would not leave the old transom in there. The water meter may not pick up moisture because it’s been inside your shop for several years. Tear it out and replace with something you know is solid.
Compressive Strenght of Coosa? Will it handle the crush of the bolts? Maybe a Backer?
Loved the thumbnail of you with the wood splitting axe asking if it was a mistake. Almost fell down laughing. 🤣
Add 1/4” stainless backing plates to distribute the load, add horizontal knees to the sides port and stbd.
Build off what is there!
Double glass the sides of Coosa and pre drill some small fill holes. After each Coosa board is tabbed in, squirt some filler in the holes starting low and going up. (micro balloons/spheres & resin?) 😃
Rip out out drive fillers. If transom wood OK leave it in place and glass in really good fit non rot replacement. Level up transom as you add another 1 - 2 inches of thickness.
Ensure all bolt holes are fully sealed with resin before sealing bolts in place. Glad it's you doing it and not me.
Why the dewaxer worked is not because of the xylene necessarily, but the fact the surface of the old glass was not properly prepared for the G10 and 5200 that was added on top. The wax on the surface of the glass then was broken down by the xylene and BAMM! No more bond and it peels off fairly easily. I have used 5200 and wiped the top off it down with xylene and not had it deteriorate.
I’d build off the existing platform being its new and dry . I tore a shabbily installed mako transom out that lasted 40 years .
I voted to rip it out just because I’d love to see how you do it. But I believe either way it will outlast any of us because I know you’ll make sure it’s better than Bertram could ever had made it.
No chance like the present one to replace. Much much easier now to go all the way. That said, a looooot more time and effort whereas you could just reinforce what is there and be 99% confident that it will be fine.
I heard ya start to quote Ave at 13.55... nice.
I would think sanding, layering another core and glassing it all in wouldn't be a bad thing. If the core isn't damaged, let it be. It was made right and sealed properly.
This part of the build I find interesting, as have rebuilt a few transoms over year's learning new, better methods allways is good.
When in doubt? Tear it out! Don't sandwich plywood behind Coosa. May be extra work and a bit of overkill. But it's done and done right.
Replace the whole thing, cons...more work and more materials, pros...you are the kind of guy that likes everything done the right way, coosa over plywood will be hammering in your head as long as you own the boat, coosa is stronger than plywood and weights less, plus it doesn't matter if by any chance you have water intrusion through the screw holes, another pro is that it will make more episodes for your UA-cam channel and that's how you are making money now, plus there are a lot of us that really enjoy your videos and the super quality work you do, all that while helping others, like me.
If its worth doing its worth over doing, given how poorly the new glass was bonded it likely that the ply is also pretty bad too.
Great video! I like mistakes, I learn a lot like I've said before! Mistakes show your not a fake! Keep up the GREAT WORK!
I think you answered yourself when you drilled the test hole and only had 1/4 to 3/8 of glass and no core. Stern Drives and outboards are two different animals when it comes to transfer of thrust to hull. Most of the sd’s thrust is low and partially thru front engine mounts. Outboards have a tendency to pull from the top and push low. Now you change the thrust vector by moving that power 1 to 2 feet back and you’ve made a pretty big lever that wants to tear the top loose from sides of the hull. Your only option is to check with the bracket mfg and get with them on how much that 3” spec must be above in relation to top mount bolts. I would also try to tie the top of the transom to side hull. Easier now than to have a failure and a “ Go Back”.
While it is additional work, i would suggest replacing because you would know it is done right and would never be an issue.
Perfection is the enemy of "It's Perfectly Fine" with your add-ons.
Just my humble opinion!
I'm not educated enough to have an answer that will help you. But as a fan I'll support your decision either way. That being said, I'd love to see this thing in the water this year.
Great video!
What type of cutting head are you using on your oscillating saw?
Replace it. You also need to add in some stringers and knees. When the boat was an I/O there was not the stresses on the transom that you now have.
I would use 1/4 coosa then layer of fiberglass till it is all level and then continue till you get the thickness you want. For the bolt holes, core out a 2 to 3" hole fill with a coosa plug and thickened epoxy to seal the plywood.
Seeing you now have screws going through it i would atleast replace where all the mounting bolts go and below them
I'd really need to know more about the engines. Do the outboard need to push against the transom? Or does most of the force go into the engine and engine beds? What does the manufacturer recommend?
There are so many inconsistencies in the current transom layup. I feel that an all new core and layup would not only be stronger but much lighter. Best of luck with your decision.