johnson compression

[steven]

what should the compression on my 1995 150 johnson be?

[Chris]

Hi Steven,

I don't have a service manual, but I believe when new, the compression rate is typically around 125.

Obviously after use, the number starts to drop off somewhat.

What you typically would be concerned about is, when there are differences which are over 10% or so, cylinder to cylinder. And obviously you would be concerned about low numbers as well, even if they are close to each other.

-Chris

[steven]

well mine is running 100psi across the board is that good?

[Chris]

It might be a little low, but there all even so that's a good sign. I know Johnson dropped the compression rates for a bit at one point as well. I think they then went back up some years later. I'm not sure if yours is one of the models that's supposed to be a bit lower.

-Chris