black gunk leaking from gearcase

[markh28]

1975 evinrude, 115 HP After running this motor in the barrel or on the muffs, I get this tar-like gunk seeping out of the prop end of the lower unit. Now I know there will be some excess unused oil/exhaust and gunk that normally comes out, because it does on my other evinrude. But this stuff is like tar. When I changed the water pump, I could see the inside of the exhaust housing is coated with it. It's almost like someone ran STP through it. How do I clean this up so it doesn't leave an embarrassing black smudge spot in the boat ramp parking lot?

 

[F_R]

Launch the boat and run it at high speed awhile. The exhaust heat will clean it up. Trying to do it on the trailer is futile.

 

[emdsapmgr]

Use a laser temp gun to check the operating temp of the powerhead once it's warmed up. The engine could be running cold. (the thermostat could be stuck open.) It's technically not a fatal problem, but a cold-running engine has poor combustion and will accumulate more tar/carbon than one that heats up properly. Since that engine uses a vernatherm instead of a more modern thermostat, it will run colder than today's outboards. I think the normal powerhead temps on that engine are from 115-130. So check the cyl temps.