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?
