That’s a great motor. I miss the classics. Much less weight. I have a 1969 red stripe 110 I am restoring that has low hours and I found a bronze two blade prop that’s new old stock that’s never been in the water. Happy boating
I got a free one from the side of the rode, it was torn apart but I didn't know what was wrong so I just put it back together and it runs fine with no problems at all
@@renn9069 yep. I grabbed it for my dad because he has a I believe its around a 12 foot Livingston. And the only engine he had was this really old 2 stroke trolling motor.
Old gal's still going well! I had 1 myself on a 11.5ft shallow v bottom. Mine went well with 1 person, but did'nt like 2 full grown up people so I upgraded to a 15hp... I regret selling it now
This motor did ok with two adults on the 12 foot boat, but it had not been used much (in storage for over 25 years according to the previous owner). I think the wiring on this vintage of 7.5s and 9.9s is critical to performance. Some interesting info has been added to the description.
@@renn9069ragazzi io ne ho uno uguale del 1979 messo veramente bene, ma ho notato che arriva la corrente solo a una candela.. potrebbe essere la centralina? visto che se sposto le bobine arriva..
@@alexanderpirone710 Ottenuto una traduzione onlune: se lo spostamento delle cose provoca una scintilla, probabilmente è un filo o una connessione difettosa. English: If moving things causes spark, it's probably a faulty wire or connection.
@@renn9069 Scusa forse mi sono spiegato male, volevo dire che all'uscita centralina alla bobina, esce solo a una,la corrente, o quella di sopra, o quella di sotto, quindi presumo che le bobine sono buone
@@alexanderpirone710 Può essere il trigger o l'altra parte di accensione. Suggerire test per un manuale di riparazione. puoi averne uno gratuitamente online all'indirizzo tinboats.net. English: It may be the trrigger or antother ignition part. Suggest testing per a repair manual. you can get one for free online at tinboats.net.
Nice! I have an 1983 long shaft 7.5 on my '80 Sears Gamefisher alum. semi V-hull. The motor runs great, but I maybe get 7mph. (Of course, that's with a 2 people, a troller, batteries, gear, and all plywood decking and floors, LOL).
I have a earlier 7.5 mercury like that. It was on my 12 foot lund. I have it in storage because i put a 4hp newer mercury single cyl 4 stroke on the boat instead. I miss the 7.5 twin though
Yes, a really nice running outboard in all ranges, and lightweight too. It was a great asset to this 12' aluminum boat. It could put a 14' boat on plane, but not with more than one adult in the boat. A 9.8 of the same vintage can get a 14' aluminum boat on plane with two adults, but not with three adults. The 14' boat referenced above was a Starcraft SF14. The SF series is a heavier gage aluminum than most, so lighter weight , shallow-v hulls, or flat bottoms may see better performance with 7.5's and 9.8's.
I have the same exact motor but a 1972 I think.but it only runs with the choke open?any ideas?when I close the choke the motor shuts down.i have a different choke then yours,it's a flip choke
Dan, Meaning the motor doesn't stay running with the choke pulled (as in the plate closes off the opening in front of the carb), right?. If not, that is what it is supposed to do. If so, then read on. The 1972 carb is different, and I haven’t worked on that specific motor/carb, but here are some general guidelines. Try to get a manual online for a diagnostic procedure and information for your specific motor. tinboats.net has many free manuals (I provided many of them), but you have to be a member with a few meaningful posts before downloading, but check. Sounds like a fuel delivery issue or dirty carburetor (or both). Could also be bad fuel. Check the easy things first. Alcohol content fuels cause debris build up in fuel lines, fuel pumps, and carbs if left in for a period of time, especially in humid environments. Try starting with fresh fuel with the appropriate oil mix (50 parts fuel to 1 part oil). If not resolved, then: The fuel line pump ball should remain firm for at least a couple of minutes. If not, check the connections for leaks while disconnected from the motor. You can spray soapy water and look for air bubbles. If yes repair and retry starting. If no leaks, but ball does not remain firm, replace ball and retry motor. If not resolved, then: Check the fuel lines from the motor-side fuel line connector to carb or fuel pump the same way (connect the tank and pressurize with the ball, then check for fuel leaking at each end of the hose). The fuel line connection at the motor will be the fuel pump (there is a screen filter behind the cover on the later motors, and a membrane-diaphragm beyond that that crates the fuel draw-pumping action). If the motor hasn’t run well in a while, take the fuel line off at the carb and see if there is free flow, if not, then clean the hose and/or connector at the front of the lower cowl, and check again. If not resolved, then: Caution gaskets and/or o-rings, and/or diaphragms may not be readily available. Sometimes these parts can be reused after disassembly. If you are willing to take the risk, then take off the fuel pump cover and check for clogs or damaged parts (a torn diaphragm is the most common damage if there is any). Clean any obstructions or debris, reassemble, then try starting. If not resolved, then: Carburetor time. Same causation as with the fuel pump: gaskets, o-rings, and other parts may not be readily available, but sometimes these parts can be reused after disassembly. Most carburetor issues on small motors can be resolved with a good cleaning by disassembling, cleaning with carburetor cleaner, and reassembling (if reusable or new gaskets and o-rings are available). If you want to do a limited inspection, check the bowl first (usually only one gasket and usually the part with most debris if any exist; and if no gasket is available, you may be able to reinstall with a fuel-resistant gasket compound). There are many UA-cam videos published on how to do this. Carburetor cleaning resolves most carburetor issues with 2-stroke engines. The second most common issue is the needle and seat (not easy to come by). If it turns out that you need a needle, message me, I know a dealer that has old ones made up, and he may have one for this motor. I’ll have to dig up the information. Hope this helps and good luck.
I also have a mercury 7.5 but my doesn’t go as fast as yours for some reason my go max speed 6mph for some reason, someone who knows maybe what problem?
Keep in mind that the boat in the video is only 12' long, and is a shallow v-hull (it weighed less than 170 lbs). The same motor pushed my heavier 14' boat more like 12mph with two people. What type of boat is your motor running at 6 mph?
@@hamzaace0229 the translation isn't clear (lathes?). For lack of revs, I'd first check that there is good spark on BOTH cylinders. I've come across many low-rev-only 2 cylinder outboards that were only running on 1 cylinder. If there is a lack of spark, check the actual wiring on this era of Mercury (the wiring including the switchbox wiring decays over time on these). if wiring is good, get a repair manual and go through the proscribed diagnosis procedure. Generally you'll need spark, compression, and fuel. Check the compression (in my opinion over 105 psi is serviceable for this motor, over 110 is decent, and over 120 is good). Poor compression usually means expensive repair. There are "reed valves" that open and close that could cause compression or fuel problems, but on this motor the reed valve assembly is configured around the crank shaft, and reed replacement requires a complete tear down (reeds are not a common problem on these outboards). If the motor was running good and then suddenly it is not, it is probably a fuel issue. For fuel issues, do the simple checks first. If there is a fuel filter, check it or remove it to see if there is a restriction. Same with the fuel lines (the fuel-line pumping bulb should remain firm - if it doesn't there is a check-valve leak in the bulb or an air leak in any of the fuel lines or tank fittings, and these malfunctions could cause lack of RPM). If fuel delivery checks out okay, clean and inspect the carburetor (dirty or malfunctioning carbs are the usual cause of runability issues). Remove the carburetor and look into the intake opening to see if you can visually inspect the reeds (can't remember if they are visible through the intake or not). disassemble the carb and pay close attention to the float (does it float in a container of fuel), and the needle valve (the needle should fall out easily when the float is removed (if the needle doesn't easily fall out, or if the tip is distorted, replace it (the needle is a common cause of lack of power or RPM - see this video notes under the title). Generally, most problems can be efficiently diagnosed by following procedures in repair manuals. Hope this helps.
Sure. I don't have this motor anymore, but I have a 1980 9.8 that has identical wiring. Email me at renn902020@gmail.com and I'll send you some pics tomorrow.
Fazir, it uses a "bayonet" style such as , Seachoice 50-20601. The original ones were metal, but the plastic ones work fine. Sorry for the delayed response.
I have one very similar to this. When i accelerate the motor revs high and the boat goes nowhere. It trolls along fine at idle or 2 mph. Do these have a shear pin? Or that rubber hub thing? Thanks in advance for any replies
Hi, I bought the exact same engine and I am very happy with it. Since I have to replace the propeller, could you give me the right measurements: pitch and diameter? Thank you very much
I think mine was a 9" diameter with a 7" pitch (9x7) , but can't be sure. If you go to crowleymmarine.com and use your serial number to search propellers, you can get the original part number, and then search ebay for a match. This is the best way to get good propellers cheap. You can also get a recommendation based on motor AND boat at Solas Propelers and Michigan Wheel Propellers with their "propeller finders" (www.solaspropellers.com/index.php/boat/prop-finder) (www.miwheel.com/outboard-propellers/outboard-sizing-analysis/). Solas and Michigan part numbers can also be searched on ebay for good prices. I've found Solas props to work as good or better than Mercury OEM. Michigan makes a lot of the OEM propellers. Good luck
@@massimilianogiannone8417 I don't have this motor anymore, but I do have a 1981 9.8 HP Mercury outboard (looks exactly the same, and is primarily the same except for the carburetor and the cylinder block porting). The 9.8 has a similar propeller, and the propeller might even be the same as the 7.5. I'll send you a pic of the 9.8 propeller.
Susquehanna River. 444 miles long, and the 16th largest river in the US. The river is artificially wide because there are 5 damns located on the lower 45 miles (roughly 45 miles), essentially creating lakes upstream and and in-between them
I sold the motor in 2017 for $575. Nice, "everything works", freshwater motors, 7-8hp easily sell for $450-$600 here. Salty, "everything works" sell for more like $300-$450 here. Motors that need work sell for less, according to the cost of repairs. 2-stroke is still very popular here - not so much in other areas.
Yes, basically a low RPM position so the motor doesn't lurch and it's easier on the hardware.. Also, be careful not to try to start without being in neutral because the non-neutral lock breaks easily. Good luck with your new motor.
It's been a while, but if memory serves, 17 mph was top speed with ideal conditions of moving calm-surface water (river-lake damned at 2 ends). I think 12 mph was reliable on the 11' boat. The high revs were likely a result of very small boat draft and load coupled with fine tuning and refreshed fuel delivery components.
@@renn9069 Ok I think it must have just been running slower due to all the weight I had. Extra person, 2 anchors, battery and elec motor as well. Gotta try it out empty.
@@renn9069 G'day mate I've just bought a small sail boat with this same motor as yours, he threw it in for free because it needs a CDI unit I think he said. I know bugger all about this stuff and any help from anyone would be greatly appreciated. He had a $499 service done on it took it once, went to take it again and it wouldn't start
@@Antipodean33 No start can be many things. Best to get a manual and go through the proscribed tests (you can get one on tinboats.net, or buy one). That being said, fuel system or spark are the most common failures. If you spray some starter fluid in the carb throat and it starts, then there is a problem in the fuel system. if it doesn't start with starter fluid, check for spark and go from there. Don't even pull the starter without being in water, or having a hose hooked up with muffs, or the water pump impeller will get damaged.
@@Antipodean33 Also, Dangar Marine, Kodibass, and Brandon's Garage have very good repair videos. I learned a lot from them. The 9.8 and 7.5 engines have the same diagnostic and repair procedures (they differ by the size of the carb. and the cylinder porting).
These really are great runners. Check the obvious: fuel lines, screen behind the line connection cap on the carb, tank line connection valve (these are very reliable, but maybe an issue). If the aforementioned are ok, probably a carb inlet float/needle, or clogged carb jets/passages. If the float does not float in a container of gas, replace it. If the inlet needle does not just fall out after removing the carb float, it must be changed (of if there is any deformation in the needle tip). This motor had an intermittently sticking inlet needle which caused a no fuel issue. this video was made after the carb work was done. The needles are obsolete, but I know where to get good reproductions for a fair price. Comment back if you need a needle.
@@renn9069 I rebuilt the fuel pump and carburetor today, all new gaskets. I pump up the fuel primer bulb and no leaks at all from anywhere. I have great compression and spark but not getting any fuel to the spark plugs (they should be getting wet on a 2 stroke with gas), I've been researching and seeing that the Reed valves could be at fault?? Also from what I read when you pull the rope starter there should not be air coming back threw the carburetor which is what is happening. Any thoughts??
Clarifications: you should feel suction if you hold your hand over the front of the carb (over the choke housing opening) while pulling the start rope. If air is coming out of the carb, that is a problem. I'm assuming that you replaced the fuel pump gaskets on the side side of the carb? Anyway if air is coming out of the carb when pulling the start rope, I'd bet it is a reed issue (could be a catastrophic crank, connecting rod, or piston issue, but you would hear metallic noises when pulling the rope, or it would be locked). Unfortunately the reeds are installed round the crank shaft and the powerhead must be pulled to service them. However, you can see some of the reeds by removing the tope end of the motor. DangerMarine has a good reed vid of a late 70's 9.8 which has the same reeds, I'd start there ua-cam.com/video/9TlKa-XBzlU/v-deo.html&frags=pl%2Cwn Stu from Dangar also answers questions - I'ver learned a lot from him. ___________________________________________ If you are getting suction and not air out, squirt some premix directly into the carb via the choke plate housing, and see what happens. If there is suction out of the carb, you could also try limited amounts of starter fluid, and if that doesn't work check the trigger and timing. if it fires, connect a container of gas (no valves - just a container and a tube) to th fuel pump cap inlet and hold the container and tube higher than th fuel pump cap and see if it runs - if it does the problem is lines, connectors, bulb, or the tank itself. Feel free to ask other questions here as needed. Good luck.
A forum I joined today a guy told me that he's seen this same issue before and the problem is the throttle limit tab that's bolted on just to the right side of the carburetor, he says take it off and it should fire right up. You ever hear of that? I'll probably try that tomorrow and see what happens. The reeds "looked" like they were shut properly when I looked threw the opening of the carburetor, but air coming out twords the carb and spark plugs bone dry is weird
Had to look at my '81 9.8 to refresh the assembly (carb is very similar). I don't recognize the tab described, but it doesn't make sense to me. If the motor is going to start short of a throttle limit, it should start if you squirt premix into the the choke housing opening. I'd try that first (confirming a fuel supply issue will eliminate other potential problems such as reeds and timing). Hope this helps.
Believe it or not, the motor actually ran well in a barrel after being in storage for over 20 years. However, it would not run past an idle when on a boat because the fuel inlet needle would become stuck in the up position when the motor was tilted backward with the natural tilt of the transom. A new needle, a carb cleaning with new gaskets, and a carful synchronization produced the result you see in the video. A bigger problem was that the wiring partially disintegrated - a common problem with this vintage.
@Zachary Morris I would get the part number by looking it up on Mercury, boats.net, or Crowley Marine, and then search that number on eBay (Crowley and mercury will show superseded part numbers, and you can search those too). Keep in mind that there are a few variations of carbs used on these outboards. If there aren't a few on eBay now, there will be soon. Once you get the carb, plan on cleaning and installing a rebuild kit. When you look for a rebuild kit, try to get a picture to make sure the kit has all gaskets and a new needle, minimally (as years go by, the carb rebuild kits come with fewer and fewer parts - I guess because some parts go out of production and suppliers are assembling out of current kits) Also, "parts motors" that would have a rebuildable carb sell around here for approx. $100. Good luck
If it’s stuck, you can try turning the propeller clockwise while moving the gear lever firmly. Clockwise as when you were looking at the propeller from behind the motor. It’s not a big deal to shift this motor while it’s not running, as long as you don’t force it and or do it often. Typically, it’s enough to turn the propeller while you’re shifting it so that problems do not occur
If that doesn’t work, you can pull the safety catch from under the starter mechanism, and tape it so that it does not spring back into the slot. Then disconnect the spark plugs and have somebody slowly pull the starter while you’re trying to shift back.
I think I got it I should be able to pull it over correct if it is in neutral. Sorry for being such an idiot I just got this outboard motor and don’t know anything about it do you know how I tell what year it is it looks identical to the one in your video
brian koop Yes, you should be able to pull the pull start to turn it over. Make sure it is in water first, or is connected with the hose attachment. Take the cover off and look for a plastic peg in front that engages the flywheel when it’s not in neutral,. Make sure it is not engaged as you can easily break it off or crack the rewind starter frame if you pull too hard on the starter rope. Don’t ask me how I know.
I assume you tried shifting while slowly pulling the starter rope? You have to take off the safety latch at the flywheel to do that , and obviously disconnect the plug wires.
@@undeafwolf179 It looks like 20 mph +, but the most I ever saw on the GPS was 18, and that was traveling with the river current. I think it delivered a reliable 14mph on this 12' long, shallow v hull, weighing less than 200 lbs.
Yes the carburetor is different, but also the block porting. I also have a 1981 9.8. The engine blocks look the same on the outside but are different (the 7.5 block has a sticker on a flat spot that says "Comet", the 9.8 has "Lightning" in raised letters that are part of the casting where the 7.5 sticker would be). Crank, pistons, head cover, reeds, and ignition are the same.
Yes, they are both weigh essentially the same. I weighed the 7.5 at 65 lbs. BTW, the lower units are also the same between the 7.5 and 9.8, but the recommended props are different. The operating RPM range is also the same, according to the Owner's Manuals.
I just got a 10ft alumacraft with that same motor. From my research, those motors are bulletproof... For lack of better words,😁
That’s a great motor. I miss the classics. Much less weight. I have a 1969 red stripe 110 I am restoring that has low hours and I found a bronze two blade prop that’s new old stock that’s never been in the water. Happy boating
Nice engine. It never failed me.
I got a free one from the side of the rode, it was torn apart but I didn't know what was wrong so I just put it back together and it runs fine with no problems at all
Ha! That's awesome. Pumped water too?
@@renn9069 yep. I grabbed it for my dad because he has a I believe its around a 12 foot Livingston. And the only engine he had was this really old 2 stroke trolling motor.
Old gal's still going well! I had 1 myself on a 11.5ft shallow v bottom. Mine went well with 1 person, but did'nt like 2 full grown up people so I upgraded to a 15hp... I regret selling it now
This motor did ok with two adults on the 12 foot boat, but it had not been used much (in storage for over 25 years according to the previous owner). I think the wiring on this vintage of 7.5s and 9.9s is critical to performance. Some interesting info has been added to the description.
@@renn9069ragazzi io ne ho uno uguale del 1979 messo veramente bene, ma ho notato che arriva la corrente solo a una candela.. potrebbe essere la centralina? visto che se sposto le bobine arriva..
@@alexanderpirone710 Ottenuto una traduzione onlune: se lo spostamento delle cose provoca una scintilla, probabilmente è un filo o una connessione difettosa. English: If moving things causes spark, it's probably a faulty wire or connection.
@@renn9069 Scusa forse mi sono spiegato male, volevo dire che all'uscita centralina alla bobina, esce solo a una,la corrente, o quella di sopra, o quella di sotto, quindi presumo che le bobine sono buone
@@alexanderpirone710 Può essere il trigger o l'altra parte di accensione. Suggerire test per un manuale di riparazione. puoi averne uno gratuitamente online all'indirizzo tinboats.net.
English: It may be the trrigger or antother ignition part. Suggest testing per a repair manual. you can get one for free online at tinboats.net.
Awesome motor..have a 1982 9.8
Nice! I have an 1983 long shaft 7.5 on my '80 Sears Gamefisher alum. semi V-hull. The motor runs great, but I maybe get 7mph. (Of course, that's with a 2 people, a troller, batteries, gear, and all plywood decking and floors, LOL).
I just picked up a 1976 merc 7.5 and with all the weight in my sterling aluminum 12ft I couldn't go much faster than 8mph.
That is one nice sounding little Merc!
Little merc setting the water on fire 👍
I have a earlier 7.5 mercury like that. It was on my 12 foot lund. I have it in storage because i put a 4hp newer mercury single cyl 4 stroke on the boat instead. I miss the 7.5 twin though
Please sell it to me dear brother..
Love that motor I wish I had one like it
Yes, a really nice running outboard in all ranges, and lightweight too. It was a great asset to this 12' aluminum boat. It could put a 14' boat on plane, but not with more than one adult in the boat. A 9.8 of the same vintage can get a 14' aluminum boat on plane with two adults, but not with three adults.
The 14' boat referenced above was a Starcraft SF14. The SF series is a heavier gage aluminum than most, so lighter weight , shallow-v hulls, or flat bottoms may see better performance with 7.5's and 9.8's.
I have got this one to i love it
I have the same exact motor but a 1972 I think.but it only runs with the choke open?any ideas?when I close the choke the motor shuts down.i have a different choke then yours,it's a flip choke
Dan, Meaning the motor doesn't stay running with the choke pulled (as in the plate closes off the opening in front of the carb), right?. If not, that is what it is supposed to do. If so, then read on.
The 1972 carb is different, and I haven’t worked on that specific motor/carb, but here are some general guidelines. Try to get a manual online for a diagnostic procedure and information for your specific motor. tinboats.net has many free manuals (I provided
many of them), but you have to be a member with a few meaningful posts before downloading, but check.
Sounds like a fuel delivery issue or dirty carburetor (or both). Could also be bad fuel. Check the easy things first. Alcohol content fuels cause debris build up in fuel lines, fuel pumps, and carbs if left in for a period of time, especially in humid environments.
Try starting with fresh fuel with the appropriate oil mix (50 parts fuel to 1 part oil).
If not resolved, then:
The fuel line pump ball should remain firm for at least a couple of minutes. If not, check the
connections for leaks while disconnected from the motor. You can spray soapy water and look for air
bubbles. If yes repair and retry starting. If no leaks, but ball does not remain firm, replace ball and retry motor.
If not resolved, then:
Check the fuel lines from the motor-side fuel line connector to carb or fuel pump the same way (connect the tank and pressurize with the ball,
then check for fuel leaking at each end of the hose). The fuel line connection at the motor will be the fuel pump (there is a screen filter behind the cover on the later motors, and a membrane-diaphragm beyond that that crates the fuel draw-pumping action). If the motor hasn’t run well in
a while, take the fuel line off at the carb and see if there is free flow, if not, then clean the hose and/or connector at the front of the lower cowl, and check again.
If not resolved, then:
Caution gaskets and/or o-rings, and/or diaphragms may not be readily available. Sometimes these parts can be reused after disassembly. If you are willing to take the risk, then take off the fuel pump cover and check for clogs or damaged parts (a torn diaphragm
is the most common damage if there is any).
Clean any obstructions or debris, reassemble, then try starting.
If not resolved, then:
Carburetor time. Same causation as with the fuel pump: gaskets, o-rings, and other parts may not be readily available, but sometimes these parts can be reused after disassembly. Most carburetor issues on small motors can be resolved with a good cleaning by disassembling, cleaning with carburetor cleaner, and reassembling (if reusable or new gaskets and o-rings are available). If you want to do a limited inspection, check the bowl first (usually only one gasket and usually the part with most debris if any exist; and if no gasket is available, you may be able to reinstall with a fuel-resistant gasket compound). There are many UA-cam videos published on how to do this. Carburetor cleaning resolves most carburetor issues with 2-stroke engines. The second most common issue is the needle and seat (not easy to come by). If it turns out that you need a needle, message me, I know a dealer that has old ones
made up, and he may have one for this motor.
I’ll have to dig up the information.
Hope this helps and good luck.
I also have a mercury 7.5 but my doesn’t go as fast as yours for some reason my go max speed 6mph for some reason, someone who knows maybe what problem?
Keep in mind that the boat in the video is only 12' long, and is a shallow v-hull (it weighed less than 170 lbs). The same motor pushed my heavier 14' boat more like 12mph with two people. What type of boat is your motor running at 6 mph?
@@renn9069 3 meter rowing boat, it doesent lathes so much on full throttle-..
@@hamzaace0229 the translation isn't clear (lathes?). For lack of revs, I'd first check that there is good spark on BOTH cylinders. I've come across many low-rev-only 2 cylinder outboards that were only running on 1 cylinder. If there is a lack of spark, check the actual wiring on this era of Mercury (the wiring including the switchbox wiring decays over time on these). if wiring is good, get a repair manual and go through the proscribed diagnosis procedure.
Generally you'll need spark, compression, and fuel. Check the compression (in my opinion over 105 psi is serviceable for this motor, over 110 is decent, and over 120 is good). Poor compression usually means expensive repair. There are "reed valves" that open and close that could cause compression or fuel problems, but on this motor the reed valve assembly is configured around the crank shaft, and reed replacement requires a complete tear down (reeds are not a common problem on these outboards). If the motor was running good and then suddenly it is not, it is probably a fuel issue.
For fuel issues, do the simple checks first. If there is a fuel filter, check it or remove it to see if there is a restriction. Same with the fuel lines (the fuel-line pumping bulb should remain firm - if it doesn't there is a check-valve leak in the bulb or an air leak in any of the fuel lines or tank fittings, and these malfunctions could cause lack of RPM). If fuel delivery checks out okay, clean and inspect the carburetor (dirty or malfunctioning carbs are the usual cause of runability issues). Remove the carburetor and look into the intake opening to see if you can visually inspect the reeds (can't remember if they are visible through the intake or not). disassemble the carb and pay close attention to the float (does it float in a container of fuel), and the needle valve (the needle should fall out easily when the float is removed (if the needle doesn't easily fall out, or if the tip is distorted, replace it (the needle is a common cause of lack of power or RPM - see this video notes under the title).
Generally, most problems can be efficiently diagnosed by following procedures in repair manuals. Hope this helps.
I have a very similar mercury thunderbolt and it is missing the kill switch. Could I possibly get a picture of where the two wires go on the motor?
Sure. I don't have this motor anymore, but I have a 1980 9.8 that has identical wiring. Email me at renn902020@gmail.com and I'll send you some pics tomorrow.
What fuel connector are u running because I have a stock male connector and cant seem to find a female connector
Fazir, it uses a "bayonet" style such as , Seachoice 50-20601. The original ones were metal, but the plastic ones work fine.
Sorry for the delayed response.
I have one very similar to this. When i accelerate the motor revs high and the boat goes nowhere. It trolls along fine at idle or 2 mph. Do these have a shear pin? Or that rubber hub thing? Thanks in advance for any replies
There is no shear pin. The propeller blade section is attached to the propeller splined section with a rubber hub.
Sounds like a spun prop. Check the hub
Getting an 81' in the morning that needs carb rebuilt. It's going on a 12ft little boat like this... What's your top speed if you know?
I think it achieved 18 mph in the best of conditions, according to gps. If I remember correctly, 14 mph was typical
top speed on a 12' boat was 18 MPH on perfect water conditions (the boat in the video). 14 MPH with a heavy-duty 14' boat
Hi, I bought the exact same engine and I am very happy with it. Since I have to replace the propeller, could you give me the right measurements: pitch and diameter? Thank you very much
I think mine was a 9" diameter with a 7" pitch (9x7) , but can't be sure. If you go to crowleymmarine.com and use your serial number to search propellers, you can get the original part number, and then search ebay for a match. This is the best way to get good propellers cheap.
You can also get a recommendation based on motor AND boat at Solas Propelers and Michigan Wheel Propellers with their "propeller finders" (www.solaspropellers.com/index.php/boat/prop-finder) (www.miwheel.com/outboard-propellers/outboard-sizing-analysis/). Solas and Michigan part numbers can also be searched on ebay for good prices. I've found Solas props to work as good or better than Mercury OEM. Michigan makes a lot of the OEM propellers.
Good luck
@@renn9069 thank you very much for your help
hello, sorry if I insist, but could you send me some pictures of the propeller of your engine? Thank you very much
Mail: gmassy@libero.it
@@massimilianogiannone8417 I don't have this motor anymore, but I do have a 1981 9.8 HP Mercury outboard (looks exactly the same, and is primarily the same except for the carburetor and the cylinder block porting). The 9.8 has a similar propeller, and the propeller might even be the same as the 7.5. I'll send you a pic of the 9.8 propeller.
WHATS THE NAME OF THE RIVER 7YOUR ON? ITS HUGE
Susquehanna River. 444 miles long, and the 16th largest river in the US. The river is artificially wide because there are 5 damns located on the lower 45 miles (roughly
45 miles), essentially creating lakes upstream and and in-between them
How much would you think it would cost? I have one and am looking to sell it
I sold the motor in 2017 for $575. Nice, "everything works", freshwater motors, 7-8hp easily sell for $450-$600 here. Salty, "everything works" sell for more like $300-$450 here. Motors that need work sell for less, according to the cost of repairs. 2-stroke is still very popular here - not so much in other areas.
You have to put the handle into shift mode to go from forward to reverse right?😁
Yes, basically a low RPM position so the motor doesn't lurch and it's easier on the hardware.. Also, be careful not to try to start without being in neutral because the non-neutral lock breaks easily. Good luck with your new motor.
What's your top speed? your 7.5 seems to hit a much higher rpm than mine does.
It's been a while, but if memory serves, 17 mph was top speed with ideal conditions of moving calm-surface water (river-lake damned at 2 ends). I think 12 mph was reliable on the 11' boat. The high revs were likely a result of very small boat draft and load coupled with fine tuning and refreshed fuel delivery components.
@@renn9069 Ok I think it must have just been running slower due to all the weight I had. Extra person, 2 anchors, battery and elec motor as well. Gotta try it out empty.
@@renn9069 G'day mate I've just bought a small sail boat with this same motor as yours, he threw it in for free because it needs a CDI unit I think he said. I know bugger all about this stuff and any help from anyone would be greatly appreciated. He had a $499 service done on it took it once, went to take it again and it wouldn't start
@@Antipodean33 No start can be many things. Best to get a manual and go through the proscribed tests (you can get one on tinboats.net, or buy one). That being said, fuel system or spark are the most common failures. If you spray some starter fluid in the carb throat and it starts, then there is a problem in the fuel system. if it doesn't start with starter fluid, check for spark and go from there.
Don't even pull the starter without being in water, or having a hose hooked up with muffs, or the water pump impeller will get damaged.
@@Antipodean33 Also, Dangar Marine, Kodibass, and Brandon's Garage have very good repair videos. I learned a lot from them.
The 9.8 and 7.5 engines have the same diagnostic and repair procedures (they differ by the size of the carb. and the cylinder porting).
Just bought this same motor last week. Has spark and good compression but isn't getting fuel for now, should be a easy fix then I can test it
These really are great runners. Check the obvious: fuel lines, screen behind the line connection cap on the carb, tank line connection valve (these are very reliable, but maybe an issue). If the aforementioned are ok, probably a carb inlet float/needle, or clogged carb jets/passages. If the float does not float in a container of gas, replace it. If the inlet needle does not just fall out after removing the carb float, it must be changed (of if there is any deformation in the needle tip). This motor had an intermittently sticking inlet needle which caused a no fuel issue. this video was made after the carb work was done.
The needles are obsolete, but I know where to get good reproductions for a fair price. Comment back if you need a needle.
@@renn9069 I rebuilt the fuel pump and carburetor today, all new gaskets. I pump up the fuel primer bulb and no leaks at all from anywhere. I have great compression and spark but not getting any fuel to the spark plugs (they should be getting wet on a 2 stroke with gas), I've been researching and seeing that the Reed valves could be at fault?? Also from what I read when you pull the rope starter there should not be air coming back threw the carburetor which is what is happening. Any thoughts??
Clarifications: you should feel suction if you hold your hand over the front of the carb (over the choke housing opening) while pulling the start rope. If air is coming out of the carb, that is a problem. I'm assuming that you replaced the fuel pump gaskets on the side side of the carb?
Anyway if air is coming out of the carb when pulling the start rope, I'd bet it is a reed issue (could be a catastrophic crank, connecting rod, or piston issue, but you would hear metallic noises when pulling the rope, or it would be locked). Unfortunately the reeds are installed round the crank shaft and the powerhead must be pulled to service them. However, you can see some of the reeds by removing the tope end of the motor.
DangerMarine has a good reed vid of a late 70's 9.8 which has the same reeds, I'd start there ua-cam.com/video/9TlKa-XBzlU/v-deo.html&frags=pl%2Cwn Stu from Dangar also answers questions - I'ver learned a lot from him.
___________________________________________
If you are getting suction and not air out, squirt some premix directly into the carb via the choke plate housing, and see what happens. If there is suction out of the carb, you could also try limited amounts of starter fluid, and if that doesn't work check the trigger and timing. if it fires, connect a container of gas (no valves - just a container and a tube) to th fuel pump cap inlet and hold the container and tube higher than th fuel pump cap and see if it runs - if it does the problem is lines, connectors, bulb, or the tank itself.
Feel free to ask other questions here as needed. Good luck.
A forum I joined today a guy told me that he's seen this same issue before and the problem is the throttle limit tab that's bolted on just to the right side of the carburetor, he says take it off and it should fire right up. You ever hear of that? I'll probably try that tomorrow and see what happens. The reeds "looked" like they were shut properly when I looked threw the opening of the carburetor, but air coming out twords the carb and spark plugs bone dry is weird
Had to look at my '81 9.8 to refresh the assembly (carb is very similar). I don't recognize the tab described, but it doesn't make sense to me. If the motor is going to start short of a throttle limit, it should start if you squirt premix into the the choke housing opening. I'd try that first (confirming a fuel supply issue will eliminate other potential problems such as reeds and timing). Hope this helps.
Je suis tellement fière de me former dans votre page !!!!!! Mais je suis désolé car vous faites parler tout en anglais
Did you have to replace the carb?
Believe it or not, the motor actually ran well in a barrel after being in storage for over 20 years. However, it would not run past an idle when on a boat because the fuel inlet needle would become stuck in the up position when the motor was tilted backward with the natural tilt of the transom. A new needle, a carb cleaning with new gaskets, and a carful synchronization produced the result you see in the video.
A bigger problem was that the wiring partially disintegrated - a common problem with this vintage.
@Zachary Morris I would get the part number by looking it up on Mercury, boats.net, or Crowley Marine, and then search that number on eBay (Crowley and mercury will show superseded part numbers, and you can search those too). Keep in mind that there are a few variations of carbs used on these outboards. If there aren't a few on eBay now, there will be soon.
Once you get the carb, plan on cleaning and installing a rebuild kit. When you look for a rebuild kit, try to get a picture to make sure the kit has all gaskets and a new needle, minimally (as years go by, the carb rebuild kits come with fewer and fewer parts - I guess because some parts go out of production and suppliers are assembling out of current kits)
Also, "parts motors" that would have a rebuildable carb sell around here for approx. $100.
Good luck
@Zachary Morris Don't use the number on the carb, use the number from a parts site. I don't have that motor anymore.
How could I get motor out of gear its in forward? Isn’t it bad to do it without the motor running I don’t want to manhandle it
If it’s stuck, you can try turning the propeller clockwise while moving the gear lever firmly. Clockwise as when you were looking at the propeller from behind the motor. It’s not a big deal to shift this motor while it’s not running, as long as you don’t force it and or do it often. Typically, it’s enough to turn the propeller while you’re shifting it so that problems do not occur
If that doesn’t work, you can pull the safety catch from under the starter mechanism, and tape it so that it does not spring back into the slot. Then disconnect the spark plugs and have somebody slowly pull the starter while you’re trying to shift back.
renn 90 gonna try now
I think I got it I should be able to pull it over correct if it is in neutral. Sorry for being such an idiot I just got this outboard motor and don’t know anything about it do you know how I tell what year it is it looks identical to the one in your video
brian koop Yes, you should be able to pull the pull start to turn it over. Make sure it is in water first, or is connected with the hose attachment. Take the cover off and look for a plastic peg in front that engages the flywheel when it’s not in neutral,. Make sure it is not engaged as you can easily break it off or crack the rewind starter frame if you pull too hard on the starter rope. Don’t ask me how I know.
I just got one today off of a customer. I can't get it in neutral.
I assume you tried shifting while slowly pulling the starter rope? You have to take off the safety latch at the flywheel to do that , and obviously disconnect the plug wires.
max speed ?
On this boat max speed was 18mph on perfect water, per GPS (12'x approx. 48" shallow v-hull).
@@undeafwolf179 It looks like 20 mph +, but the most I ever saw on the GPS was 18, and that was traveling with the river current. I think it delivered a reliable 14mph on this 12' long, shallow v hull, weighing less than 200 lbs.
I was wrong serial number is 4250250 doesn’t start with a its a 4
Think it might be 75
He could trim it up a notch and perhaps a slightly higher pitched prop.
Stroken!
That thing is fast
Susquehanna river , Wrightsville Bridge ?????? I`d bet on it !
Yes. Really nice at night too.
i think the only difference from the 7.5 to 9.9 was the carb
Yes the carburetor is different, but also the block porting. I also have a 1981 9.8. The engine blocks look the same on the outside but are different (the 7.5 block has a sticker on a flat spot that says "Comet", the 9.8 has "Lightning" in raised letters that are part of the casting where the 7.5 sticker would be). Crank, pistons, head cover, reeds, and ignition are the same.
renn 90 You know your mercs.... i wonder about weight
renn 90 I would imagine it would be the same
Yes, they are both weigh essentially the same. I weighed the 7.5 at 65 lbs. BTW, the lower units are also the same between the 7.5 and 9.8, but the recommended props are different. The operating RPM range is also the same, according to the Owner's Manuals.
renn 90 if i buy a 7.5 i may shrink the main jetting and run C12 make it as fast as a 9.8 lol