compression on a 15 hp mercury

[huntergreg]

Just wondering if anyone could tell me what the compression should be on a 1995 mercury 15hp. I have 96lbs in both cylinders. The motor runs great. I was told it should be 125lbs in each. 

[FC]

Did you test with the throttle open? should be about 125-130 if it's a 2 stroke and probably 180-200 if it's a 4 stroke. Proper test is with engine warmed up and throttle open.

[huntergreg]

I did the test when it was cold. I put the tester in the plug holes and just turned it over. Does warming it up make a difference?

[FC]

I did the test when it was cold. I put the tester in the plug holes and just turned it over. Does warming it up make a difference?

Yes, the rings expand and seal up a bit better, opening the throttle gives more consistent results and is the standard way to check compression.