96 50hp Mariner acts like prop is slipping when full throttle. prop repair or engine

USMCDon

Recruit
Joined
Jul 25, 2013
Messages
2
I have a 190 22' pontoon boat with a 96 50 hp Mariner 4stroke engine. At full power the engine will suddenly rev very high. After throttling back to idle, the engine will pull the boat ok. Return to full speed and it happens again. I brought the boat home and checked the prop. Cant turn the prop without turning the motor over by hand. Can't seem to get the prop to slip at home. Do I have a prop slipping or does the engine have a clutch that might be slipping? Does it even have a clutch?
 

pootnic

Chief Petty Officer
Joined
Aug 11, 2007
Messages
447
Re: 96 50hp Mariner acts like prop is slipping when full throttle. prop repair or eng

Is your prop coming out the water?
Maybe your motor isn't low enough...
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: 96 50hp Mariner acts like prop is slipping when full throttle. prop repair or eng

Its certainly not unusual for a pontoon to have ventilation(cavitation) issues.
You can test the prop by putting a waterproof line across the hub and do a test run and note if the line is broken .
What size prop? the numbers are near the base of the blades or under the prop nut.
Have you tried lowering the trim a notch?
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,811
Re: 96 50hp Mariner acts like prop is slipping when full throttle. prop repair or eng

You may be ventilating which is the prop is sucking in air around the plate above it called the anti-ventilation plate.....neat huh!

If you have trim, trimming in will help which means tuck the lower unit closer to the boat. If you are sitting too high on your engine bracket and can drop the engine down a hole (3/4") that will help. A cupped prop will help. If all else fails, a thing called a Whales Tail will force the surface air to take a longer route to your prop and can solve the problem.

HTH,

Mark
 

USMCDon

Recruit
Joined
Jul 25, 2013
Messages
2
Re: 96 50hp Mariner acts like prop is slipping when full throttle. prop repair or eng

I took the boat out to the lake and trimmed the motor down . Runs like a champ. Thanks , guys. I used to be better than this. Getting old I suppose.
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: 96 50hp Mariner acts like prop is slipping when full throttle. prop repair or eng

Ain't it wonderful when we hit the nail right on the head?
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,811
Re: 96 50hp Mariner acts like prop is slipping when full throttle. prop repair or eng

Ain't it wonderful when we hit the nail right on the head?

Isn't that why we do it. Why else. Grin

To kill time for us retired gurus when you can't go outside and play with your toys......marine and agricultural.

Mark
 
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