Dried soot in engine compartment.

[Danush]

What could be cause? I noticed a flex tubing came apart but was told it did not have to do with exhaust but likely the air conditioner.

 

[Terry Cox]

Ditto here. Likely from the engine belt.

 

[DayDreamer41]

I would say its more likely belt dust, not soot. Is it more predominately at the front end of the engine? Soot means smoke, smoke means odor and a high likely hood of CO, means really bad things could happen.

 

[SG]

Beyond the tight belts or overly loose ones, sometimes the return air from the engine gets cycled through from the stern.
How much? Is the problem new?

 

[Benny17441]

Oil fumes escaping the engine combining with belt dust.

 

[bawlmer]

Don't discount stray exhaust. Back in 2015 I started to notice small amounts of soot in my engine compartment. Then after docking after a 2.5 hour motoring trip the engine compartment was an unholy mess of soot. What happened was a very small hole started to form in the exhaust riser. This was from internal corrosion. I did not notice it through the nice red paint job the PO's mechanic applied. That accounted for the small amount of soot. Then the hole got a lot bigger (1/4") one day and blew soot everywhere. Four years later I am still finding sooty places and cleaning them.

 

[NotCook]

I’m betting a belt. When was it last replaced? Is it very old? Is it new, but the wrong size, or too loose?