Lets see: 27 year old engine, used 4 or 5 months a year so call it 100 engine hours, Call ir 3000 hours on the engine. And given the age it is probably raw water cooled.
Question 1 is white smoke or black smoke? Black smoke would be soot/unburned fuel. Could be a cold cylinder head (lets see, Lake Superior gets up to something like 45F in August, right?), an incorrect or misfunctioning thermostat that is letting too much bypass water flow and prolonging warmup time, or pump or injectors starting to wear and overfueling the engine. In that case the black smoke would tend to go away after the engine gets to operating temp and combustion is more complete. Depending on the engine hours, if the rings are getting worn you could have reduced compression, which would cause some incomplete combustion after the glow plugs are turned off until the engine block and head come up to normal temperature. White smoke is coolant. A possible case would be an early sign of head gasket failure. A very small amount of cooling water getting past the head gasket will flash into steam (white smoke) and as the block and head expand with heat, the gasket will seal and water will stop. Is there a chance that the engine has 4 or 5,000 hours on it? If so, it might be prudent to retorque the head bolts to ensure a tight seal of the head gasket. With a more pronounced head gasket leak, especially with a FWC engine, pressurized hot water will seep into the cylinder after the engine is turned off and seep down into the oil pan. An early sign would be foam and gray sludge in the oil, in addition to a big puff of white smoke when the engine starts. Engine would still start, but would tend to run rough . On a FWC engine you would see antifreeze coming out of the overflow bottle as the engine runs, but on a RWC engine you would not notice much until the leak became bad enough to cause a water lock and an engine that would not crank. Not sure if any of that will help. But it may give you a place to start when troubleshooting. Rick Brass Washington, NC From: CnC-List [mailto:[email protected]] On Behalf Of Fred Hazzard Sent: Wednesday, May 15, 2013 5:55 PM To: [email protected] Subject: Re: Stus-List Overheating due to plugged knuckle Rick: My 1986 4 cyl Yanmar smokes a bit when first started. After about 5 mins of motoring at about ¾ throttle it smokes very little. An thoughts from your experience with these Yanmars? I have no idea of the hours as the hour meter was broken and showing 1100 hours when I bought the boat in 2007. This engine starts very easily and runs well. Fred Hazzard S/V Fury C&C 44 Portland, Or
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