[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.

[JB]

Not good. A 10-15% spread is the standard. 25% is too much, but 100psi is too high to be a badly damaged cylinder.

A good decarb might well bring that in line.

[Josh122593]

thanks i took i to the lake last night and i cudnt barley pass idling speed without it bogging down and me n my dad adjusted the carbs a little bit but it didnt do n e gud so ill just put the new carbs on the motor

[Josh122593]

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

[JB]

I use water, but that is risky. I suggest you use Seafoam.