1987 3.0L OMC Cobra - loss of power

[Ryan09]

Boat: 1987 Peterborough Monza
Motor: 1987 3.0L OMC Cobra (I/O)

Problem: The motor revs high and loses power when a load/drag is released

I first noticed this happen last year when I was trying to ski with one ski (if I was using two skis everything was fine – might be coincidence) behind the boat. I would start in the water, the boat would begin to move forward and pull me behind, as soon as I was able to stand up and get out of the water (in my mind this is the “release” point of the load/drag) it was very apparent that the motor would rev significantly higher and it would lose all forward power but the motor would stay running.

When I got the boat out for the first time this year (not skiing) a very similar thing would happen. I would throttle up to get the boat moving but as soon as the boat would get on plane (again, I see this as the moment when the high load/drag is “released”) it would rev high and lose all forward power. On one occasion the boat died after the rev and loss of power but started back up immediately when I turned the key – motor seems to run well.

Has anyone experienced this before? Any information you could provide would be greatly appreciated!

 

[southkogs]

Welcome aboard: long shot, 'cuz it's not quite acting right for it - but is your prop hub moving on you? It might be letting go.

 

[Ryan09]

Thanks for the reply! It doesn't seem like it is moving on me. Ill try to take the prop off, mark both sides, and then run it a bit to see if the marks change locations relative to each other. Is that the best course of action?

Side note: is it possible that it is the gears in the lower unit? That's one of my thoughts, but I'm questioning myself because I would have thought that there would be an issue when there is "load" and not when it is "released"

 

[southkogs]

Correct: mark the hub and the prop and then check for movement.

It doesn't sound like a gear issue to me. Is your lube clean and free of a lot of metal? Maybe there's something going funky with the shift or throttle cable, but that doesn't quite seem right yet.

 

[Scott Danforth]

prop hub or coupler would be first guess.

 

[Lou C]

If it was the lower gears you’d hear and feel a pronounced clunk when accelerating. Sounds like prop hub (hope it’s that) or engine coupler (lots more work to replace)...

 

[Ryan09]

Thank you all for the comments. I hope to look at it further this weekend. I will be sure to update this thread once I've figured it out.