sludge from behind the propeller

[romeomart]

I have a 1981 Mercury 650 3 cyl., every time I run the engine, I get a small black residue sludge from behind the prop section, is this normal from old engines or is there a bigger problem lurking?

 

[haventaclue]

If it's black and smells like burnt oil,normal.It's just the exhaust sludge,when engine is at running temperature it softens and runs.

 

[racerone]

Fairly normal on 2 stroke engines.----Some of the oil / gas goes right through a conventional 2 stroke motor.