I know this is an old thread, but, I have the same issue…….
Just traded my brother for a 1969 9.5hp Evinrude that has been sitting for over 10 years.
It has spark, turns over "freely" with the pull start . . .
but, it only has 40psi compression. I am thinking of equaling out the cylinders and put
in some sea foam, one ounce twice a day and see if that loosens up the rings to get better numbers.
Is this the way to go ? or use another fluid like ATF/Acetone mix, PB Blaster, etc.
I really don’t want to start taking this motor apart.
I will build a motor stand this week so I can put it in water and try to get it running.
I read the other posts about 5oz oil and sea foam to a gallon of gas . . . will try that too if it runs.
I would really like to see 80+psi.