My teenage son and I are refurbishing a 1982 Evinrude 7.5 hp. We honed the cylinders and replaced the piston rings. The problem is we?re only getting 78 psi in each cylinder, with the new rings. So I?m guessing they were rebored at one point and we need to put in oversized rings. My question concerning compression is? (Assuming both cylinders are the same compression). What is the minimum acceptable compression for a 7.5 hp. motor to work?
Update: pulled the head cover and the cylinders spec standard. 80 psi seems low to me for new rings. We put new rings on a 1977 Johnson 55 hp. last summer and the compression went from 100 to 140+ on each cylinder. Don't understand why a 7.5 hp. should be a whole lot different.
Update: pulled the head cover and the cylinders spec standard. 80 psi seems low to me for new rings. We put new rings on a 1977 Johnson 55 hp. last summer and the compression went from 100 to 140+ on each cylinder. Don't understand why a 7.5 hp. should be a whole lot different.
