Cavitation and Ventilation are two very different scenarios. In most cases, it is as you noted having the propeller ingesting air from the surface causing loss of thrust. Cavitation occurs when the propeller compresses the water to such a high PSI that the temperature exceeds the boiling point and a gas bubble is formed. Both can cause damage to the propeller face. Someone somewhere named the “anti ventilation plate “ incorrectly and caused all the fuss. Thanks for posting this. Many many boaters could use some guidance on proper mounting and trim. Not to mention the right prop for the boat to start with. Engineer Jeff.
Actually cavitation occurs when the propeller decompresses the area in front of the prop to a low PSI which lowers the boiling point of the water getting sucked into the propeller. Higher pressure would increase the boiling point such as with pressure cookers that increase pressure to keep the liquid from turning to steam, keeping things moist during cooking.
its funny because to me the first thing you want to check is the propeller conditon and rpm at wot ... i had a damaged 9.5 x 10 prop on my 15hp evinrude wich was spinning way too much for my 128 pounds wide kaboat ...changed for a brand new 9.25 x 12 and ventilation disapeared except when i hit 2 feets waves a full throttle it will catch some air but running full throttle in those conditions is not confortable anyways so going 3/4 throttle in those condition prevent it. Another i need to do is add at least 1 additional psi to each tubes and 2 psi to the keel and floor since the water in my area is kinda cold and must drop my psi below ideal pressure thus not cutting the waves properly. I am not sure an hydrofoil would let me hit 2 feet waves full throttle anyway, maybe help me keep the nose down when alone but its almost never the case because I always sit someone in the front. Thanks for the video man.
My issue is the new 25 mercury I purchased with a new 14 ft. Princecraft . It’s a 20” long shaft . 2023 , both models. The outboard when clamped down on the stern puts the ventilation, or anti ventilation plate two inches to low . It should line up with the lower keel @20” no? . I spoke to a mercury tech. and was told they measure from the inside of the clamp down to the lower unit bolts and not the ventilation plate . Most new small craft boats and some old have either 15” or 20” transoms . Why are the mercury small outboards 2” to long . Before it was stolen, I had a 25 four stroke Yamaha ( brand new) on the same boat a the fitment was just right , with in a half inch. Forgot to mention , I played around with the trim and jacked the motor up . By doing that it looses all its integrity not to mention it looks just wrong . Maybe one of those fins bolted would help .
The fixes you describe have nothing to do with cavitation or the boiling of water due to a low pressure area. What you are trying to fix is ventilation which is pulling air from the surface into the propeller. That plate on the motor is an anti ventilation plate. This is the same sort of thing when people say quite instead of quiet, or loose instead of lose. Wrong description.
Hi, you are right, it’s technically the wrong description, but the reality is people refer to this issue in the inflatable boat industry as cavitation. We are suggesting fixes for their Issues. I explain it’s actually ventilation we are fixing in the video.
Cavitation and Ventilation are two very different scenarios. In most cases, it is as you noted having the propeller ingesting air from the surface causing loss of thrust. Cavitation occurs when the propeller compresses the water to such a high PSI that the temperature exceeds the boiling point and a gas bubble is formed. Both can cause damage to the propeller face. Someone somewhere named the “anti ventilation plate “ incorrectly and caused all the fuss. Thanks for posting this. Many many boaters could use some guidance on proper mounting and trim. Not to mention the right prop for the boat to start with. Engineer Jeff.
Agree with everything except that water is not compressable.
Actually cavitation occurs when the propeller decompresses the area in front of the prop to a low PSI which lowers the boiling point of the water getting sucked into the propeller.
Higher pressure would increase the boiling point such as with pressure cookers that increase pressure to keep the liquid from turning to steam, keeping things moist during cooking.
@@1985wolfmanI agree with this.
its funny because to me the first thing you want to check is the propeller conditon and rpm at wot ... i had a damaged 9.5 x 10 prop on my 15hp evinrude wich was spinning way too much for my 128 pounds wide kaboat ...changed for a brand new 9.25 x 12 and ventilation disapeared except when i hit 2 feets waves a full throttle it will catch some air but running full throttle in those conditions is not confortable anyways so going 3/4 throttle in those condition prevent it. Another i need to do is add at least 1 additional psi to each tubes and 2 psi to the keel and floor since the water in my area is kinda cold and must drop my psi below ideal pressure thus not cutting the waves properly. I am not sure an hydrofoil would let me hit 2 feet waves full throttle anyway, maybe help me keep the nose down when alone but its almost never the case because I always sit someone in the front. Thanks for the video man.
Prox was here
My issue is the new 25 mercury I purchased with a new 14 ft. Princecraft . It’s a 20” long shaft . 2023 , both models. The outboard when clamped down on the stern puts the ventilation, or anti ventilation plate two inches to low . It should line up with the lower keel @20” no? . I spoke to a mercury tech. and was told they measure from the inside of the clamp down to the lower unit bolts and not the ventilation plate . Most new small craft boats and some old have either 15” or 20” transoms . Why are the mercury small outboards 2” to long . Before it was stolen, I had a 25 four stroke Yamaha ( brand new) on the same boat a the fitment was just right , with in a half inch. Forgot to mention , I played around with the trim and jacked the motor up . By doing that it looses all its integrity not to mention it looks just wrong . Maybe one of those fins bolted would help .
The fixes you describe have nothing to do with cavitation or the boiling of water due to a low pressure area. What you are trying to fix is ventilation which is pulling air from the surface into the propeller. That plate on the motor is an anti ventilation plate. This is the same sort of thing when people say quite instead of quiet, or loose instead of lose. Wrong description.
Hi, you are right, it’s technically the wrong description, but the reality is people refer to this issue in the inflatable boat industry as cavitation. We are suggesting fixes for their Issues. I explain it’s actually ventilation we are fixing in the video.
Still dont know anything about ventilation cavitation. Try include driving sounds next time. SHOW DONT TELL!