I have a 1986 15 HP which has been running perfectly until recently. I
hadn't used it for two years and not knowing anything about outboards
except where to start and steer. The motor overheated while cruising
and it shut down and became very hot.
Some hot oil was forced through one of gaskets. I brought the unit to
a repair shop and they told me the impeller was gone so it overheated.
He measured the compression which is now 80 lbs and 85 lbs. He told me
that the motor would be too expensive to repair. Could it be that a
blown gasket is the reason for the now low compression. The cylinders
look fine to the eye. I'm thinking about buying a shop manual and
trying the impeller and gasket replacement.

Any thoughts?