Yanmar 2GMF and black smoke

[Doug]

We start and shut down our engine as specified in Yanmar's owners manual. That is to say...we give full throttle to start and then back off immediately. And to shut down (after 5 minutes at idle) we give it full throttle and then pull fuel cuttoff followed by turning off key once it stops. My question is..how much black (or dark gray) smoke should emit from exhast when we do this. It does not start hard (fires right up every time) nor does it smoke while running but at start and stop it gives us a bit of a cloud. Is this normal? We get good water flow so I would believe our mixing elbow to be clear. You veteran Yanmar/diesel users out there could probably help me, I hope.Also, for your 1988 33.5 owners, do you notice that with more than one person toward aft end of cockpit that the exhaust through-hull is under water (bottom couple of inches of transom) and that you hear bubbling as if water is blocking exhaust. Could this cause problematic backpreasure? anything to worry about? It seems Hunter put that exhaust exit in a precarious position. Let me know please. Thanks.Doug

 

[Steve Dion]

BLACK MAGIC

Doug:The black smoke is an indication of TOOOO much fuel. Under normal operations the throttle would be opened slowly and the fuel would get burnt accordingly. When you rev this engine quickly, you are just giving it more fuel than you can burn in the alloted amount of time. We do not let our engine idle long after arriving at the dock. I am usually slowing down as a get closer to the harbor and then the couple of minutes that it takes us to get to the dock plus tying it off seems to be enough to cool down the engine.As far as the exhaust under the transom, many if not all the Hunters are built this way and the have survived. It would be nice to know if there is water comming out but I guess that is what the sounder is for. It sounds off a long time before the engine is over-heated to give you an adequate safety margin. But your concern is the same as most other Hunter owners on this note.

 

[john edwards]

the smoke

Ahh the smoke problem. We have had the same problem and it is definitelty that to much fue is being dumped into and not being burned up. adjust the governr arm at the fuel injector where the cable moves the fuel arm. Also the diesel needs to heat up to combust properly check your thermostat in the engine to ensure she is not worn out etc. The bubbles are fine they go great with fish entrees

 

[Bryan C.]

It's normal

Particularly for a 10 year old engine, its normal to smoke when you rack it up. What's happening is that too much fuel is being dumped than can be burned until the RPMs pick up. Also, if you have been running it at low RPMs (should cruise at 75-80% rated RPMs) you may be blowing out some built up carbon. It it starts easily and doesn't smoke under normal cruising conditions I wouldn't worry about it.