Re: Black water comes from Onan 11 exhaust hose

Mike Ondra

Hello Jose.
We had similar carbon discharge from the Onan during spring start up, powder as well as chunks of carbon. Ultimately the Onan would not start. Opening up the exhaust mixing elbow revealed huge carbon buildup leaving only about 1 cm diameter air passage for the exhaust. Not at all uncommon when marine diesels are not run periodically under high load. That would be the first place I would look.
Mike Ondra
Aletes SM 240

On Aug 22, 2019, at 8:45 AM, Mark Erdos <mcerdos@...> wrote:



Can you give more information? Is it when you start the Onan or all the time? Is it oily or carbon? What model Onan and boat is this on? How you done anything to troubleshoot and if so what were your findings?



With best regards,





Sailing Vessel - Cream Puff - SM2K - #275

Currently cruising - Vista Mar, Panama


From: [] On Behalf Of Jose Alegria
Sent: Thursday, August 22, 2019 2:43 AM
Subject: [AmelYachtOwners] Black water comes from Onan 11 exhaust hose


Dear AMEL Group / Owners
I appreciate your ideas about the reason I have black water comes from my onan 11 raw water exhaust hose 
And from exhaust fumes too  ( less quantity )
The Onan was 1200 hours and was serviced at 100 hours
Thanks in advance


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