I posted an article last month about white smoke coming from my 3HM35F Yanmar engine and promised to update the forum after it went in to be fixed. To recap, we had white smoke from the engine. It got progressively worse under load from say 2100rpm onwards. The engine did not overheat, there was no loss of power and no loss of coolant. However, you could see what looked like a stream of unburnt fuel coming out of the (wet) exhaust. When our engine guy first tested it, he said he couldn't find anything wrong so he asked another Yanmar engineer who said it would be a small crack in the head gasket. The head gasket was replaced and the injectors cleaned. When I rang to check on the progress, the engine guy said the machinist confirmed that the head gasket had blown in two areas. I was relieved as the research I had conducted (see below) listed numerous potential causes. We used the boat yesterday (the engine guy didn't have time to test it under load and we wanted to use it over the long weekend) and (you guessed it) the white smoke problem is still there - exactly as it has been prior to the replacement of the head gasket (although the stream of unburnt fuel has now gone). My previous research has produced numerous causes for white smoke including: a) blown head gasket b) timing c) bad fuel d) bent rod e) loose hoses f) burnt valve seats g) water in the fuel h) fuel cetane rating too low I'm going to try a cetane additive to eliminate (h). If anyone has any other ideas I would greatly appreciate hearing them.
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Steam?
Could be your engine is running hot and vaporizing some of the seawater in the heat exchanger (and out the exhaust where you see it). I'm assuming a fresh water cooled engine. Do you have an analog engine temperature readout? Check your engine temperature. The problem could be with a partial blockage in the mixing elbow or in the seawater pickup. Check the volume of water flow out the exhaust. Does it look like it is reduced from before? I pulled the hose off my mixing elbow and ran it into a bucket while running the engine. It was very slow. Growth had partially blocked my through hull. Not enough seawater could cool the fresh water loop and was turning to steam. I had to push it for a while then the high temp alarm went off. Alternatively if the flow is good, remove the thermostat and run for a short while and see if the white smoke dissapears. If so, the problem could be a bad thermostat,Don't run without the thermostat for a really extended time (hours) as it will be too cold and that increases engine wear.
Could be your engine is running hot and vaporizing some of the seawater in the heat exchanger (and out the exhaust where you see it). I'm assuming a fresh water cooled engine. Do you have an analog engine temperature readout? Check your engine temperature. The problem could be with a partial blockage in the mixing elbow or in the seawater pickup. Check the volume of water flow out the exhaust. Does it look like it is reduced from before? I pulled the hose off my mixing elbow and ran it into a bucket while running the engine. It was very slow. Growth had partially blocked my through hull. Not enough seawater could cool the fresh water loop and was turning to steam. I had to push it for a while then the high temp alarm went off. Alternatively if the flow is good, remove the thermostat and run for a short while and see if the white smoke dissapears. If so, the problem could be a bad thermostat,Don't run without the thermostat for a really extended time (hours) as it will be too cold and that increases engine wear.
Cool temps?
David, I don't know where you are sailing, but this early in the season you may be seeing vaporized water (steam). You know how your car looks like it is blowing smoke in the winter and then after the air temp warms up there is no smoke? Diesels can do the same "illusionary smoke".
David, I don't know where you are sailing, but this early in the season you may be seeing vaporized water (steam). You know how your car looks like it is blowing smoke in the winter and then after the air temp warms up there is no smoke? Diesels can do the same "illusionary smoke".
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