Trying to bring back to life a 1993 Yamaha 9.9 HP 4-Stroke that has water in the oil. Been sitting unused for years. I can get it to run but not too good. Sounds like it is running on 1 cylinder. Top cylinder has 140 PSI. Bottom cylinder 75 PSI. Drained the old oil in it and put in new and it became contaminated right away. Dropped the lower unit and hooked up a pump to the water pipe and pumped water to the motor to see if it would get into the oil (drained the oil). No water came out of the oil drain plug? Also it does not smoke or miss when running?? Cylinder head gasket? What other terrible thing could be wrong?? Thanks ..........