Re: 1970 115 hp evinrude compression
It's considered acceptable to have cylinder readings within 10% of each other. Your 85 reading is outside that "normal" range. It is also normal to have one head's readings up to 5 lbs difference from the other head, based on factory machining techniques. Before you tear into it, you might want to try an application of Bombardier's Engine Tuner. It cleans the combustion chambers and rings of carbon-possible the compression might come up a few lbs. Usually an older engine will idle/run better after the application.
