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Exhuast Snot

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jn1440

Contributing Member
Got a 1999 Evinrude 9.9 HP ling shaft used as a kicker for a sailboat. Its got a strange issue where its full of this oily snot like looking substance, basically what you get when you mix gear oil with water and shake it up. It isn't a small amount either, its layer on the entire exhaust system and drip out the prop. My initial thought was a seal in the lower unit had failed but no water in the gear oil and no visible leaks. All of the "snot" is in the exhaust passage none near the input shaft or output shaft, it coats it all the way up to the power head. This one has me stumped has anyone had a problem like this before?
 
It's probably just oil and gas mixture combustion byproducts. Is engine running normally? Is she running warmer than usual? Pull plug and inspect, Is plug super clean,pure white? Possible water intrusion, gasket issue, Try a compression test to verify if gasket is intact.
 
jn1440 we need a little more history on your engine, Is this a new issue? How old is she? Are you running correct mixture?
 
Unfortunately I don't have much history on it as its a new to me engine. Got it attached to the sailboat so I imagine it's been pushing that boat it's whole life. I use fresh gas and 50:1 mix wit fullsynthetic penzoil the handful of times I have run it. It runs well other than the trail of snot. Plugs have normal wear no oil build up and compression is within 5% on the two cylinders. Usually it runs at half throttle.
 
Check your WOT rpms pushing the barge. If you can get a prop with less pitch you can then blow out the cobwebs. One of those timing light tachs will tell you if your lugging the motor for sure but I bet your just over propped. If the motor is too low in the water it can also cause it to load up with too much back pressure you want the cavitation plate about five inches below the water line.
 
​jn1440, what is the model number of your motor? Isn't a 1999 9.9 Evinrude a 4-stroke? If it is, and you are running mixed gas, well there is your answer.
 
Either way you need to give it a good decarb or two to clear out the engine and exhaust system. That would be funny if it is a four stroke I wouldnt feel to embarrassed tho. Life is a learning curve speaking for myself that is not very high on the list for stupid stuff. Just give it a good decarb and then tune up/ oil change. Then take it for a test drive.
 
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