Re: Evinrude Compression
Love the popcorn photo!
Most of my 25hp OMC's get about 125psi (on MY gauge)---my '99 30hp Johnson had only 125psi the day I bought it and still has 125psi today and runs like a top.
I would say 90 psi is low, but the fact that they're even is what makes me suspect that your gauge may be inaccurate. The big question to me is how does it idle?
I have a mercury 65hp that I just disassembed. It had 140psi on the top, 140psi in the middle, and 130psi on the bottom cylinder. The top cylinder was fine, the middle had only 1 functional ring--the other 2 rings missing 2 inches of the ring on the exhaust side, and the bottom had 2 out of 3 rings stuck in the grooves. So, compression can definitely be misleading.
If it idles nicely I'd say your gauge is wrong. No need in jumping to conclusions since compression gauges are notorious for being inaccurate.
If you can't get it to idle, I'd check it with another gauge before I sunk money into it. Taking off the intake bypass covers and looking/feeling the rings on each piston to see that they're free and see how much scoring you have on the pistons is awfully easy and cheap. I rarely break a gasket when taking off the bypass covers.
JMO,
JBJ