[Josh122593]

What is piston compression supose to be on a mercury 90 hp sport jet 3 cylinder?I tested it today and it was top-125 middle-100 bottom-120.Greatly appreciate any help.

[jim_b_20653]

125 is good. What is more inportant is that they should be equal. It sounds like you may have stuck rings. You should decarb, then restest the compression, hopefully the numbers will look a little better.

[Josh122593]

thanks do u use sea foam to decarb if not what do u use

[JB]

Duplicate post. See Merc.