Motor cavitating on pontoon boat

[Total Chaos]

Motor cavitating on pontoon boat

I have a friend who bought a palm beach 22ft pontoon boat with the 22" pontoons instead of the 19" standard pontoons. He also upgraded from a 90hp Suzuki to a 115 Yamaha. When we go out in it and even turn slightly the motor cavitates bad. The motor is trimmed down all the way. Even going straight if he trims it up any it will cavitate. I'm saying the shaft is too short. It's mounted down as far as it can go. The dealer says it's not the shaft but it's propped wrong. It has a 17 pitch. They're telling him to go to a 13 pitch. I'm not buying that. What do you guys think?

Total Chaos

[rolmops]

Those extra 3 inches will make a difference,but shifting the weight on the boat farther towards the back can make a difference. Trimming the engine all the way down is not good because it will push the bow down and the stern up. You want to try to raise the bow a bit, that will bring the outboard a bit deeper. As for changing the pitch? I would say BS

[PhlyanPan]

Yeah I've never heard of changing prop pitch affecting how deep it runs in the water.  Sounds like hoey to me.  

 

Ask the dealer if he's willing to bet the prop on it.  He gives you the prop he thinks will work.  If it does, you pay him for it.  It it doesn't....

[offshore]

A good dealer would have water tested and proped the boat correctly in the first place

[John E Powell]

Is it cavitating or ventilating? They're not the same thing. Generally speaking, some newer prop designs are engineered to be able to work closer to the surface than other designs. I would take the dealer at his word about the prop their suggesting and give it a try with the understanding that if it didn't operate correctly you can return it undamaged for full refund.


Sent from my iPhone using Lake Ontario United

[slow rollin]

I am a marine tech and I rig new pontoons on a daily basis and your problem is any one of these 3 things and can be all 3 .  Wrong prop, engine is mounted in the wrong holes( typically Yamaha is mounted in second hole down) or incorrect shaft length for the boat. Which can be fixed by adding a jack plate. If the boat is new take it back to the dealer.  Pm me if you have any questions. Hole this helps