60 HP Prop Cavitates

[hotmod]

I have a 1994 60 Hp Mercury on an 18' pontoon & at times you can be running down the lake at full throttle & with just small chop the motor will rev up for a second & then catch again. I have had the prop hub checked & it is ok.
The trim tab is missing from this motor & I am wondering if the open cavity could be causing this. I have also been told that a Hydra-foil might help solve this.

any help would be greatly appreciated.

 

[Chris1956]

Re: 60 HP Prop Cavitates

That motor sounds like it is ventilating. See if the antiventilation plate is at the level of the water, when on plane, or how much above the water it is. You may need to drop the engine lower on the transom.

It is doubtful the missing trim tab has any effect. it acts as a anode, so you should replace it.

 

[hotmod]

Re: 60 HP Prop Cavitates

The anti-ventilation plate is just at the top of the water or slightly above (according to the load on the boat) when at speed, so this may be the problem. It is worse when the boat is heavily loaded & worse if any load is toward the front. The motor is set as low as it can go, so would a manual jack plate be a good solution or is it possible that adding a hydra-foil might add enough surface area to eliminate the problem.

Thanks for your help.

 

[Chris1956]

Re: 60 HP Prop Cavitates

I cannot speak about adding a fin, as I have never used one. A manual jackplate would help. Sometimes a prop with more cup will work as well. Does your current prop have any cup? I would think any prop after the early 70s would be cupped, however,

 

[lncoop]

Re: 60 HP Prop Cavitates

This one might be better off over in pontoons.

 

[mgjtkt]

Re: 60 HP Prop Cavitates

Also look in the propeller forum.