96 15hp evinrude compression question

[Gus]

We have a 1996 15hp two stroke Evinrude that just doesn't seem like it has all the power it did prior to an overheat.

Story, borrowed it to someone who swears nothing happened but the motor overheated. I know the impeller was less than 2 years old. Upon disassembley the impeller was basically gone. I don't know if sand was injested or if the impeller really just bit the dust in less than 2 years. Anyway, the motor was run to overheat point for a decent amount of time.

Replaced impeller, motor starts and idols fine. Just doesn't seem to have the power it did. Compression reads 91psi on top cylinder and 90 on bottom. Only difference is the top will hold 91 while the bottom slowly loses the pressure. Maybe 1 psi per second on the dial.

First of all, is 90 psi too low for this motor? Secondly, is the dropping pressure a big concern?

Wondering if I need to tear it apart and look for problems?

[boatfixer]

I would take the head off and have a look. There are plenty of engines running these days with 90 psi in both cylinders. The dropping does concern me a bit though. When you take the head off, look for scoring in the cylinder walls. Its also very possible the heat expanding things to the point where the head gasket lost its sealing abilities. If there is no scoring, use a straight edge to look for warping on the head. If you dont find scoring or warpage just replace the head gasket with a new one and see what happens.

[Gus]

Thanks for the reply. I think I will do just what you suggested. Winter will be here before we know it and what good is a heated garage if you can't use it.

[delcecchi]

One thing that will toast an impeller is to run the motor out of the water, even for a very short time. Some might think that if you turn it off quick so it doesn't overheat that it would be ok, but it's not.