89 omc cobra i/o wont go over 2500 rpm

[67stanger]

Have a 89 omc i/o deck boat and my wuestion is whats going on with the boat not goingbover 2500 rpm at full throttle. Carb rebuilt and still can get it to go over that max and only doing about 15mph at tops. Also cant get to plane out

 

[southkogs]

Two fast checks before I vote: 1) Didja' check your prop hub? and 2) what kinda' compression are you getting?

Welcome aboard!

 

[Silvertip]

Is the engine firing on all cylinders. It is amazing how many people cannot tell when an engine is misfiring. If it is running on all cylinders, is it making full power? My guess is that it is not making full power due to (but not limited to): 1) throttle not opening fully, 2) improperly adjusted ignition timing, 3) overall poor engine condition or 4) boat is water logged to name just a few

 

[notstock4long]

I had the same problem a couple of days ago, and changing the fuel/water separator fixed the issue. I was stuck at 2000 RPMs but that's all I changed, and it was back to full RPMs, although there is still a lack of speed issue.

 

[67stanger]

Changed prop and still same issue. Also changed fuel separator when first started working on it about a year ago even in neutral throttle bounces between 3500 and 4500. And sorry about the vote part still learning about posting here.