Loss of power at speed

[Mikejr]

Been at the lake for nearly 3 weeks and boat has been running normally and reliably. Today before taking kids for a ski was running across the lake and the engine would lose power and rev. Or when I pushed throttle it would sound lime it does when cavitating. I quickly headed back to the dock.
checked plugs, oil gear lube etc and all seem normal. Engine starts and revs at dock with no load just fine.

We have two days left and I’d love to find a simple fix. Any ideas for trouble shooting on the water or trailer(assuming I can get to the ramp)?

 

[Alumarine]

The quickest test would be to change the prop.
How's the engine temp?

 

[Mikejr]

The quickest test would be to change the prop.
How's the engine temp?

No temp changes - was watching that. Don’t have a prop to change over in the lake but will pull
it off once the boats on the trailer and let you know. . Thanks!

 

[Rick Stephens]

No temp changes - was watching that. Don’t have a prop to change over in the lake but will pull
it off once the boats on the trailer and let you know. . Thanks!

Two places where there is rubber in the drive train - the prop hub and the coupler at the back of the engine. Either one can fail making a loss of power, or a complete loss of power. The hub is most likely if you are not overheating at all. But either is possible.

Note: never go boating without a spare prop.

 

[Mikejr]

Two places where there is rubber in the drive train - the prop hub and the coupler at the back of the engine. Either one can fail making a loss of power, or a complete loss of power. The hub is most likely if you are not overheating at all. But either is possible.

Note: never go boating without a spare prop.

So an update on this problem. I decided with two days left to just pull the boat and get it on the trailer. On my short run to the ramp (-1mile) I tried to recreate the problem. Nothing. Couldn’t get it to repeat across a range of speeds and amounts of push on the throttle (ie hard/soft etc).
Once on the trailer I pulled the prop off hoping to see a blown hub...but it was solid.

so my question is could the engine coupling be an on and off problem or would it be consistent?

 

[Tassie 1]

What motor etc etc is it??

 

[Rick Stephens]

I doubt a coupler would come and go. Now hat you are on the trailer, pop the top on the outdrive and take a peek at the upper gears. Might be possible to chew those up and be intermittent before a failure.

 

[QBhoy]

Can’t think why I’m the only one that thinks this might be a simple case of cavitating perhaps ? How high were you trimmed up ? Is the trim perhaps getting moved by accident?

 

[Mikejr]

I’m certainly hoping simple cavitation. Trim was not up but maybe not fully down either. I’ll check top of the leg in the morning.
huge thanks guys!

 

[Bondo]

I’m certainly hoping simple cavitation. Trim was not up but maybe not fully down either.

Ayuh,..... Had you just through some weeds,..??

 

[Mikejr]

Ayuh,..... Had you just through some weeds,..??

Good question. Not weeds but I was in the middle of a bunch of small debris and ‘crap’ that had moved together from the Wind. What would that do?

 

[Boater31]

I had a similar situation last year. Trimmed the drive all the way up and found a stick that got logged in the cavitation plate but above the prop. Removed stick and worked normal. If you couldn't recreate the problem heading to the ramp and can't see any damage. I think I'm going with cavitation as well. You can try Rick's suggestion to be sure, or run it again and if no problem, done.

 

[Mikejr]

So been back on the water 2x now and pulled kids etc. Problem seems to be resolved. Odd but I’ll take it.
huge thanks for all the ideas.