Exhaust smoke

There are three types of smoke that can come out of the exhaust. White, Blue and Black. None of it is good. In general the color of smoke indicates the following:

  • White means water in the exhaust. Could be water in the fuel or a leaking head gasket, in which case your coolant water enters the combustion chamber in your engine. So check your fuel and the level of coolant water.
  • Blue means engine oil is being burned. Area’s of concern are worn valve seals, piston rings or turbo charger.
  • Black may indicate worn fuel injectors or a worn turbo

I had a serious smoking generator exhaust of my 11kw Fischer Panda. White smoke…. But there was no consumption of the coolant water. So it could only be a sea water problem. I checked the following:

  • impeller
  • impeller blade strainer
  • strainer
  • through hull
  • engine temperature
  • exhaust temperature
  • windings temperature

Everything was fine, only the exhaust temperature was a bit higher than before. Not much though. 48 degrees against 42 normal. For steam (white smoke) you need 100 degrees.
I just could not find it. Hired a diesel mechanic. He confirmed after listening and looking at the generator that it was fine. But it was smoking… He insisted that there must be something wrong with the seawater cooling. He then systematically started to take things apart. Starting at the water intake. Took the hose off and opened the through hull. Barely water was flowing into the boat. But I was sure that the intake was clear. He then removed a non-return valve that was installed directly on the seawater intake valve. HUH? Who puts a non-return valve before a strainer?? Well it was the culprit. Jammed with sea weeds. But letting just enough water through to prevent a cooling water alarm, but enough to create steam. I checked every single engine part with a temperature gun (like the ones they aim at your forehead to see if you have a Covid fever) and found nothing to be hotter than 75 degrees. So I don’t understand where the steam is formed but it did.


  • Make sure that you write down the normal numbers for future reference.
  • You must not run diesel engines at low RPM. It then does not get hot enough and the engine will wear out quickly and clog up with soot. Especially the turbo does not like this. When I run my generator to charge my batteries, I always switch on the AC’s to get to a minimum load of 50%. Higher load would be better but I don’t have enough gadgets yet……