[Devil_Inside]

OK I know that this is a long shot, but hopefully someone will be able to help me... I will be looking at a Mercury engine tonight (not sure what year) and I wanted to do a compression test, but I am not sure how much compression it should have to be healthy... All I know is that it is old, 65 HP, 2 stroke, 2 cyl (?)

I had a 1983 Johnson 60HP and it had 150psi on the top cylinder and barely 30psi on the lower...I know what that means and that is why I am looking for a new (used) engine.

My guess for the Mercury would be 120-150psi with less than 10psi difference between the cylinders...is that right?

I have attached a picture if that helps.


Thank you!!!!!!!!!!!!!!!!!!

[studlymandingo]

Above 100 on all cylinders, no more than 10% variation between cylinders. I personally would like to see numbers above 115.

[jddenham]

It's a four cylinder, and around a 1970 model.