What prop

[big6six]

Ok in august I bought a used 2005 starcraft 20ft holliday fishing pontoon boat 2005 40hp elpto mercury and single axle hustler trailer. all still look new 8,000 for all I thought i was getting a great deal and to some point i still do. The problem is the tach wont settle on this thing when it runs right with 1,000 pounds and 20 gallons of fuel . WOT rpm is 5300 but often goes up to 6000 and back down and the prop seems like is slipping all the time. If just me and my son are on board it slips as soon as i start off and i trim up the motor at all it will slip very badly the moter still looks new I took the prop off to see what it was and this is what i have F12.5 X 8P this is my first pontoon and the family loves it hope i didnt buy a dud. Is this the right prop for this boat or should I change it and if so change it to what for best all around performance.

THANKS
BIG6SIX

 

[bgbass.1]

Re: What prop

sounds like your motor isnt far enough into the water and your grabbing air.

 

[Silvertip]

Re: What prop

Or the prop has a spun hub!

 

[DMAN1968]

Re: What prop

Hello,

More than likely it's prop ventilation that's getting you there. My 24 foot Lowes pontoon boat with a 48 johnson SPL does the same thing. I have it lowered to the lowest possible setting and it will still blow out easily. I would try lowering the motor to it's lowest setting and see if that will help the situation.

Mine came with a hydrofoil and i took it off to see if that affected it. The problem only got worse so i put it back on. Maybe a hydrofoil would be helpful in your case.

If that doesn't do it...well...I'm still trying to solve that issue with my own. Hopefully someone else here has another idea.

 

[Frank Acampora]

Re: What prop

See! You're saying that with a load it runs well most of the time. With a load, the pontoons are sitting lower in the water and so is the engine. With no load--just you and your son-- the pontoons ride higher and the engine ventilates right away. SO; lower the engine if at all possible and move some weight to the stern to lower the back of the pontoons into the water more, and thus also the engine. Maybe even investigate notching the transom to get the engine lower---CAREFUL! a little goes a long way. do it in increments. Or. purchase a jackplate so you would have a lot of adjustment.

Maybe investigate cost and availability of an engine leg extension--sort of like a sailboat aux. engine leg. Sounds like you really need to bury the prop deeper in the water.

 

[Silvertip]

Re: What prop

Some props are more efficient than others (within the same pitch range) so you might try one with more blade area or even a four blade. Check with a local marina. Many provide a try before you buy program and for just a few bucks.

 

[kenmyfam]

Re: What prop

Does sound like you need more motor in the water...but as said previously, check for a spun hub.