Hi I am gonna test a outboard mercury 200 from 1987 tomorrow.
What is normal compression on that engine? (warm, and with the throttle full open, a new battery)

Regards Jonas

Jonas You will get more response on this question at scream and fly.com My best guess is around 120lb with no more the 10% difference

That might be ok compression if the motor's fresh I think it should be higher mine had cut heads and it was 160

usually towards 130-135,and on an outboard 5lbs variance is the rule for a "good" motor!

if that motor shows 120 it's in good shape

An 87 finger-ported 2.4 should show 120 to 130. As was said, 5 lbs variation is acceptable.

You can cut the heads to 145 with no worries on pump gas, but above that you'll need to remove the ignition advance module (it just unplugs).