1982 Evinrude 90hp oil leaking

[shallow hull]

Just went down to the dock to check on the boat. Saw oil leaking down one side of the motor, see pics. '82 Evinrude 90hp E90TLCNB. Has not been run for a couple of weeks. Motor has been running good (except for clutch dog beginning to slip).
Didn't have time to pop the hood. Anyone have an idea of what the cause could be?

 

[racerone]

Could well be the gasket between the powerhead and the exhaust housing.----If it has never been replaced it might be due.---Factory gasket is metal re-inforced and the best option.---Any pictures inside the cowling at the joint ??

 

[shallow hull]

Not yet. I just went down to look but didn't have time to take it off.

 

[emdsapmgr]

Racerone nailed it. Esp about the metal gasket. Running the engine this way is not a prelude to imminent powerhead failure. The problem is that the black tarry substance also comes with exhaust smoke. This smoke will fill the inside of the cowling while running and the engine will re-ingest that smoke down the carb throats. That's really not what you want going back inside a clean engine.