I have a 1997 Merc 9.9 HP 4 stroke with about 25 hours on it and was told the rings had frozen in from lack of use, I'm not a mechanic but I took it to a guy who works on motors and we did a compression test with the carb off. Did it twice and both times I had 153 PSI in both cylinders, we then squirted a little oil in the cylinders and did it again, 153 PSI. Squirted more oil into the cylinders and re-did the test and 153 PSI again in both cylinders. Sounds good, but what should the compression be for this motor? I've been told anything over 120 PSI is good just so they are even. Any thoughts anyone on what the compression numbers should be?
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