compression test 1986 90 hp

[lstring]

i have a 1986 90 hp johnson outboard.i ran a compression test after warm up and came up with these results. left bank top 115 bottom 110, right bank top 120 bottom 105. i have always went with 15 lb difference rule , i'm sure that would apply here .correct me if i'm wrong. model # j90tlcdc motor has loss of power on top end. thanks

 

[joereeves]

Re: compression test

The 15 psi difference would worry me, especially if a top end problem existed. I'd suggest you remove the cylinder heads in order to inspect the pistons, cylinder walls, sealing surfaces of the head and block, and the underside of the cylinder heads.

A few psi diffrence has been found to be of no consequence BUT when the difference starts upwards to say 10 psi difference, a major problem is usually in the making.

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