1975 Evinrude 25hp Compression ???

[cajun66]

I performed a compression test on my 75 Evinrude 25hp and got 90psi out of both cylinders. This motor seems to be running good now with a new fuel pump installed. But just out of curiosity, I did a compression test on one of my 1974 Johnson 25hp parts motors and got 120psi out of both cylinders. Is my Evinrude worn out? What is a desireable compression #?

 

[The-Machinist]

Re: 1975 Evinrude 25hp Compression ???

I would try a decarb with seafoam, and test it again. Cant make it any worse

 

[tashasdaddy]

Re: 1975 Evinrude 25hp Compression ???

agree on doing the decarb with seafoam. but the good news is that they are equal, and will probably keep running. may be a little hard to start. the decarb, has been known to free up carbon coated rings, and increase compression.

 

[cajun66]

Re: 1975 Evinrude 25hp Compression ???

I use Seafoam as an additive at work all the time (diesel Mech). But I have no clue how to decarb a boat motor. But I did get it to run and used it last saturday. Made a 14 mile run. I'll check the compression again.

 

[cajun66]

Re: 1975 Evinrude 25hp Compression ???

OK. read the post on how to de-carb a motor using seafoam. I checked my compression after my 14 mile run and saw 100psi in both cylinders. Performed the de-carb and am now reading 125psi in both cylinders. I'm definitely a believer now.

THANKS!!!!