white smoke in exhaust

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White smoke is often steam. Are your engines using any coolant or running hotter than normal?
 
What causes white smoke in the exhaust of a 135HP Lehman?
Nothing good. Its either water vapor due to overheated exhaust or its incompletely burned diesel fuel.
Easy things to check:
Water flow out of the exhaust.
You should be able to hold your hand on the exhaust hose downstream of the riser and the riser itself.
Clean seawater intake strainer.
Heat exchanger sea water side blockage.
Worn out sea water pump/impeller/missing blades.

Diesel fuel in exhaust will have a strong smell. Water vapor, not so much.
Rebuild the fuel injectors.
 
Loofoo: I see you’re from Bourne, MA. Is this recent? With a seasonal change meaning cooler weather, the exhaust may look like like smoke but could be steam from when the water hits the exhaust gases. Does it quickly dissipate?
 
My FL 135 constantly produced white smoke. In addition, after shutdown it would leave a fuel sheen in the water near the exhaust. In my case both problems turned out to be associated with the thermostat. Apparently most FLs were shipped with 165* thermostats. As such the engine never reaches full operating temperature. Fix for me was to swap out the 165* for a 180* thermostat. No more smoke trail and barely a hint of diesel in the water. Everybody is happy. I hope your problem isnt any more serious. Brian at American Diesel can explain it perhaps far better than I can.
Cheers,
-David
 
Nothing good. Its either water vapor due to overheated exhaust or its incompletely burned diesel fuel.
Easy things to check:
Water flow out of the exhaust.
You should be able to hold your hand on the exhaust hose downstream of the riser and the riser itself.
Clean seawater intake strainer.
Heat exchanger sea water side blockage.
Worn out sea water pump/impeller/missing blades.

Diesel fuel in exhaust will have a strong smell. Water vapor, not so much.
Rebuild the fuel injectors.
Plan to install rebuilt injectors this winter.
 
Cold air = “white smoke.”

Use the search, this crops up every fall/winter.
 
I agree, but you have to read Tony's article on white smoke which is only one of several articles on that page. Here is the direct link to the article: https://www.sbmar.com/articles/what-is-white-smoke/

In the OP's case a block heater will help mask the underlying problem. That problem is probably one of these that were listed in the article:

1. Poor fuel quality (low cetane rating).
2. Low inlet air temperature.
3. Low coolant temperature.
4. Low compression ratio.
5. Retarded (incorrect) ignition timing.
6. Incorrect/failed fuel injection components.

But heat will almost certainly minimize the problem and is a lot cheaper than fixing many of the real problems.

David
 
Check for puffing blowby at hot idle. Checks for poor compression in one cylinder.
 
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