[619618]

I was looking at a 1990 mercruiser 170hp and found that the #2 cylinder had compression of 175psi. The manual says it should be 150, and the other 3 cylinders were 150-155psi.
Does anyone know what would cause a high compression?

 

[thefishingfreak]

high compression

maybey to much oil in the cylinder fogging oil etc.for winter storage?
some folks use oil to beef up the compression when they sell there older motors oil seals the leaky rings tempararaly

 

[leakyrivot]

If you fogged that engine before you checked compression and haven't run it to burn the oil out, yes, that is normal. Fogging oil puts the compression through the roof. The high compression could also be carbon build up, it might be time for a de-carb; even four strokes can benifit from a decarbing, just never use decarb on a deisel.

Jon