9.9 Yamaha Black oil stuff out of prop hub?

grewvin1

Petty Officer 2nd Class
Joined
Apr 2, 2012
Messages
189
Yamaha, 9.9 MSHX, 1999 engine. Just bought it from a guy and ran it to test and there is this black oil (exhaust smelling) dripping out around the prop and out of the center of the prop hub. Need Ideas if this is a problem with the engine or over oil to gas mix?
 

robert graham

Admiral
Joined
Apr 16, 2009
Messages
6,908
The exhaust goes out thru the prop/hub, and being a 2 stroke motor naturally there will be burned oil/carbon residue there....
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
But it should not be liquid carbon.

Either fuel pump is leaking dumping too much fuel into crancase or a cylinder is not firing properly and burning the fuel in it

after a sea-foam decarbon of the motor there is a lot of crude that will flow out of the exhaust
 

robert graham

Admiral
Joined
Apr 16, 2009
Messages
6,908
If the previous owner stored the motor laying on it's side then the fuel/ oil mix may have leaked down through the motor and out the exhaust....best way to see if there's a problem(and I doubt there is one) is to put the motor on a boat and run it down the river for a while wide open throttle....when you get back take a look at the prop hub.....Put fresh fuel in the motor when you run it since old gas won't run well and could produce smoke, etc...
 
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