• Registered: 2011-07-21
  • Posts: 21

Topic: Wet exhaust water is black

Everyday I'm happier and happier with my Co26. She is the perfect size and her systems are just complicated enough to allow me to figure out how to fix them while learning about them.

Today I went to pick up my boat which I had put away in a protected inlet in which she could ride out Irene. There was no wind so I had to motor. When I checked the water exhaust in the back of the boat to make sure that the water pump was working I noticed that the water was blackish in color and seemed to have a bit of smoke mixed into it. The more gas I gave the motor the darker the water.

Two weeks ago some jelly fish clogged the fresh water intake for the motors cooling system. As a result my motor quickly overheated, the cabin filled with blue smoke. I checked the motor after this happened and found that my Vetus water lock exhaust had started to melt so that all the wet exhaust was gushing into my bilge.

I bought a new water lock exhaust, installed it. Today was the 4th time I used the motor since the installing the exhaust.

I've know very little about diesel motors but I'm thinking I might need a oil filter. I did change my oil a month ago but did not change the filter.

Has this happened to anybody, any input would be greatly appreciated.


The motor is a 6hp Kubota.

  • From: Petit Rocher NB Canada
  • Registered: 2009-12-15
  • Posts: 55

Re: Wet exhaust water is black

Hi Bernard,
Trouble shooting section of the Beta manual (Beta being essentially the same motor as the Kubota) does not mention black exhaust water. It does indicate that black exhaust gas might be caused by an over pitched propeller-engine will not reach its full rpm. Solutionsuggested: Get the propeller re-pitched. This being said you would probably have noticed the condition before. Could it simply be that Irene stirred up a muddy black bottom in the inlet? I take for granted that you have a strainer to prevent most debri from reaching the heat exchanger. If not it would be good insurance to install an inline strainer that can be easily cleaned. That's my 2 cents worth of advice but definetly the best advice I can give you regarding your motor is to call Beta Marine in North Carolina. The kind gentlemen knows his engines inside out.

...)))) May the wind fill your sails and the sun shine in your face cool
  • Adrian
  • Adrian
  • Administrator
  • Offline
  • From: Toronto, Ontario, Canada
  • Registered: 2005-04-18
  • Posts: 542

Re: Wet exhaust water is black

Black smoke from a diesel engine is indicative of an engine that has reached peak torque under heavy load, and is having more fuel dumped into the engine. The black smoke is unburnt or incorrectly burnt fuel. The general solution is to back off on the throttle.

That said, I can't say for sure this is what's going on with your engine.

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