I have a 79 model Evinrude V4 (85hp). I've had it about 2yrs now. The motor is all factory (yes, it really is) and it's have little to know work done on it. When I first got it, it tested ar 120psi on all four cylinders.

One cylinder has dropped compression and the more you run it, the more it drops. I've stopped running the motor now and I've even replaced the head gaskets (they were factory sealed still!) but the cylinder is still around 50-55psi whereas the other 3 are at 120psi.

I was told that you could shoot some 2-stroke oil into the cylinder, run a pressure test and if your psi increases to the expected pressure (120psi), then your rings are bad. I did this and the psi instantly shoots up to 120psi.

Does this mean that I need to simply replace the rings or rebuild the motor? Obviously, I will have to have a mechanic mic the cylinder wall to see if it's out of round or warped. I just wanted to get some opinions based on experience with this before going to a mechanic to have the motor checked and getting quotes.

Most mechanics are telling me "rebuild" and most are saying $2,000-3,500. While I can understand, it's a lot of trouble to take apart a motor, replace a ring, and then when something else goes wrong, they could be viewed liable so they want to simply rebuild it and know that the motor won't come back to them (for warranty work).



Modified by Ozark Angler at 4:26 PM 1/11/2011