I was doing some tune-up work today with the boat out of the water, using a hose-fed container full of water for the cooling. The container allowed the water level to be just above the intake openings, and some exhaust water and steam would make contact with the water in the container. After about an hour of total running, I noticed a very thin film of dark greasy residue around the water line and above(where the exhaust vents) on the sterndrive. Also this same residue was floating on top of the puddled water outside the container. Do I have a bad seal in the sterndrive that would allow gear oil into the water intake line, or is this normal? I hope so. 
