Black substance coming from prop

[TruDaddy]

Black stuff coming out by the exhaust/prop, and it appears to be overheating. Ran it at 1500 rpms on muffs and it wanted to stay at temp halfway b/n 145 and 220.

 

[Bt Doctur]

either the engine is burning oil, there would be a lot of smoke or the outdrive oil is leaking, or it was heavily fogged down for winter.

 

[stonyloam]

If it is running hot, that indicates you are not getting enough cooling water into the exhaust, and you might be burning up the rubber on the shutters and bellows, or it is running rich. In any case the overheat indicates it is time for a new impeller.