1988 evinrude 110hp - compression

I am looking at a boat with a 1988 evinrude, I asked about the compression and here are the results I was given:


starboard block upper-115, lower-120

port block upper -108, lower108

and new water pump, intake strainer and plugs done a well.

Is this reasonable ?

No.....

I would want to see that myself - it's very easy to do and easy to lie about or even rig. For starters adding something as simple as some engine oil to the cylinder can falsely raise the reading.

With that said, carbon can falsely raise or lower compression - once I went to look at a pair of engines, found the compression to be 60 PSI on a couple cylinders and I walked, a buddy of mine bought them anyway (were really cheap but I wanted runners and not parts), got them running with a little tinkering, and the compression jumped up to an even 90+ psi. It turned out the owner was honest and they really were "good"..

Anyway - so if you want a good reading ideally I pull out the plugs, spray WD40 into the cylinders (to clean out any excess thick oil and provide a little lubrication if it's dry in there), then turn the engine over with the plugs out to blow out excess oil/lubricant. Then I crank for a good few seconds and check the gauge on each cylinder, then I run the engine and re-test. Using a real procedure you might find the compression ends up much more even and there's nothing to question.

Those readings would be perfectly good on an engine you own - they will run perfectly well like that. What might concern me a little is why the 12 psi difference. Probably is carbon/oil/gunk related (high cylinder false reading) or a little minor scoring on the lower testing cylinders or carbon sticking the rings. If you were really serious about the boat you could request they pull the heads and exhaust bypass covers for inspection, isn't much $$ in gaskets or labor. If the head bolts won't come out easily you don't want the engine anyway.

Jon

A good decarb may help that compression.