I just did a complete powerhead rebuild on my 1980 Johnson 35 HP. I had it bored .030 oversize and replaced pistons and rings. I've put it together and have run it at idle on the work stand for about 20 minutes. I've checked the compression and I'm getting 110 in one cylinder and 120 in the other. This seems low. I would expect about 135. I'm concerned about my boring job possibly being a little undersize. When I placed the rings in the cylinders to check end gap, I got .007, which is what I think the minimum is. Being concerned about broken rings or, worse yet, broken lands on the pistons, I pulled the head. The cylinders are beautiful.
Is it possible that I just need to run it some more? I really hate pulling the power head on this motor, but if I do have a problem with rings and I score the cylinders, the motor is toast. Opinions please.
Is it possible that I just need to run it some more? I really hate pulling the power head on this motor, but if I do have a problem with rings and I score the cylinders, the motor is toast. Opinions please.
