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Discussion Starter · #1 ·
My boat has a Yanmar 8HP 1GM10, pretty great condition and up until now i would swear this engine is bulletproof. Recently i noticed that after starting, the engine spit out a black discharge from the exhaust for about the first 5 - 10 seconds of running. After that, it goes away and doesn't re-occur until i restart the engine after it has cooled. I understand that diesel engines are rather inefficient and sometimes expel un-burnt fuel and such out their exhaust. I guess what i am wondering is, If this is normal why would it just start to get worse now? If this is not normal, what would cause this?

Thanks in advance...

:captain:
 

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Black is inadequate fuel burn. Either caused by too much fuel, or too little air or poor combustion.

Some random thoughts.....How clean is your air filter? That's the first and easiest thing to check. A bad spray pattern from dirty injectors could cause poor combustion. Does your motor have a glow plug and is it working?
 

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the 1GM10 has no glow plug it has a pre combustion chamber. if the injector is worn and leaking by fuel will accumulate in the chamber and cause the black smoke on cold start.. best to just change the injector with a new one. a new one is $100 and a rebuilt one is around $80
 

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Discussion Starter · #6 ·
Thank you for all your replies...

Off to the Marina in the AM to do some investigating...

More to come...

Geoffrey Roeser
 

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Black is inadequate fuel burn. Either caused by too much fuel, or too little air or poor combustion.
....... OR, COLD combustion chamber. The relatively high thermodynamic efficiency of a diesel engine is dependent primarily TWO things: high pressure (compression) AND relatively high temperature of the combustion chamber.
If the black smoke is not noticed after the engine is fully warmed, you're probably 'over-fueling' (via too much 'throttle') a COLD engine.

That stated, check the condition of your fuel injector .... first!
Any 'injector shop' can evaluate it for you. Any 'large' town in the US typically has at least one 'injector shop'.
 

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A dribblely injector can easily be ignored after it warms up a bit and the black smoke stops but it can be slowly blowing a hole in your piston top and wearing out the rings
 
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