25 hp -(low speed/boat loaded -Cavitation problem)

[tkess987]

I recently purchased a 1988 High Tide- (duck hunting, gigging)
Boat runs great- seems lose grip(cavitate?) when getting up to speed, but does catch relitively quickly and will go fast- !!That is only when I am in it by myself....

But, when boat is loaded down, with three people it will not even think of getting on plane. Its chugs along. Seems like it is not gripping? Prop is beat up pretty good. its a 10 1/2 x 13 I had a mechanic tune up and ride with me after purchasing and he recommended a 10 1/2 x 11- based on the slow to get up and go issue...

I trust my mechanic(I would not use him otherwise) That being said, it never hurts to get a second opinion before I buy the wrong prop. Anyone have an opinion on the proper prop for my setup. Lastly I would like decent top end, but good low end for running the boat with it loaded down(duck hunting etc..)

Thanks

 

[Bondo]

Re: 25 hp -(low speed/boat loaded -Cavitation problem)

I trust my mechanic(I would not use him otherwise) That being said, it never hurts to get a second opinion before I buy the wrong prop.

Ayuh,...

Considering that He was There,+ We aren't,...

I'd think that His recommendation is the Best place to Start....

 

[steelespike]

Re: 25 hp -(low speed/boat loaded -Cavitation problem)

You may have a ventilation problem,cavitaion is a different problem.
if its venting motor will rev way up and boat will slow.
Really need more info on the boat and motor.2 stroke,4 stroke,Brand?
Your beat up prop is probably struggling.You may be able to get it repaired and run it for more accurate info.If a prop change is necessary keep it for a spare.Also important to have actual rpm and speed.A tiny tach is reasonable,easy to install and will fit any similar motor without regard to stator poles.buy or borrow a gps.only way to make an accurate selection
for best motor health and efficient operation.A 13" prop is slightly toward the high end but not excessivly so.

 

[tkess987]

Re: 25 hp -(low speed/boat loaded -Cavitation problem)

Thanks for the info. The Motor is an 1988 Johnson 25 hp - 2 stroke.

 

[Moody Blue]

Re: 25 hp -(low speed/boat loaded -Cavitation problem)

My GUESS is that you are over-propped. I had a 14ft with a 40hp on it and was running a 10 1/2" x 13p prop to pull waterskiers. Started with a 15"p but had no hole shot. Top end speed was great though. Changing from 15p to 13p made a world of difference.

Since you are running a 25hp with a fairly heavy load I would opt for the lower pitch and sacrifice top end speed. As mentioned, you really need a tach to see what the engine is turning at. You don't want to exceed the top end RPM range.

Some marine supply houses will let you try out props before committing to buy. Maybe that is an option for you if you know of one locally?

The other possibility is that the prop hub is spun (broken loose from the prop) and that is allowing the shaft to spin inside the prop. WHile the prop will still turn, it will slip under load and be very ineffective.

 

[tkess987]

Re: 25 hp -(low speed/boat loaded -Cavitation problem)

Thanks again for the great info!!