View Full Version : Yanmar 1GM10 bluishwhite exhaust smoke

05-16-2007, 01:46 PM
"I bought a 1989 8-metre sailing yacht with a Yanmar 1GM10 in July 2006. I had the engine serviced a couple of months later - oil and filters changed. I used it quite a lot since then (location Mediterranean) and it always started easily and worked well. I only used to notice a little light grey smoke emitted from the exhaust, with no noticeable loss of engine oil. A few days ago, however, the engine started emitting bluish-white smoke as soon as I switched it on and, upon checking the engine oil after a couple of hours motor-sailing, I noticed that the level was reaching just above the half-way mark on the dipstick. The oil on the dipstick was black, with no sign of water or diesel in it. This emission of bluish-white smoke happened all of a sudden - in the sense that I had not noticed a progressive increase in exhaust smoke before. I have used the engine a couple of times since then - it starts and works perfectly, but the bluish-white smoke has increased further. No bluish-white smoke however, is emitted while idling, although the exhaust water leaves an oily slick on the water. As far as I know, bluish-white smoke indicates engine burning oil, thus the decrease in the oil level, and this could be due to piston/rings problems. Are there any other possible causes for this? Would further use of the engine (with engine oil topped up, of course) cause damage? In other words, is this a question of immediate engine surgery? Thank you and best regards."

05-16-2007, 02:46 PM
"Assuming that the engine is getting plenty of air i.e. clean air filter and unrestricted air flow. Some of the likely causes of white smoke are; bad injectors and or injector pump. If the fuel is not atomized properly it puddles and does not mix with air properly. Excessive unburned fuel can also wash out badly needed lubrication to the piston rings that reduces cylinder compression and burns oil. If the fuel system checks out, you may have a bad head gasket or cracked head or leaky cylinder sleeve seal if so equipped. If so, the white smoke is caused by water or coolant being burned in the cylinder. This will also cause reduced lubrication to the rings.
Continued use of the engine will cause more serious damage.
I hope this helps"

05-16-2007, 08:48 PM
"blue smoke is oil burning and white is incomplete combustion. This engine must be run at 3000 rpm, it is made for that RPM . You should attain 3600 under full throttle with the right prop. See if this is what is happening. Adjust valves to .008 thou, both & cold. Make sure fuel filter is good and you do not have algae in the tank. ie Take fuel sample in small clear glass jar. Put in sun, if it turns black you have algea. Clean tank and use a biocide. You may have got some bad fuel.
On thing I hve found in the past, take off the alt belt and run the engine. I have see alt short out and cause load. This wee engine can not run a bad alt and prop at the same time.
let me know. Regards Ron"

05-22-2007, 03:57 PM
"First of all, thanks for the two replies to my first message. Re fuel - I have taken a sample in a small clear glass jar and left it for hours in bright sunshine. Fuel remained perfectly clear. So no fuel problem exists. Called a marine diesel mechanic for diagnosis. As soon as I started the engine, we noticed a noise which was not present before. Mechanic also noticed air pressure coming out of the opened oil filler cap. He stopped the engine immediately and said that the problem was most probably coming from piston rings. Engine will now be taken off boat to check rings and any other additional (hopefully not) problems."

05-10-2008, 09:50 PM
hello I have a yanmar 1gm10 runs very well but after a number of hours I need to top up oil. exhaust smoke is a little white engine knocks loudly not sure if this is normal for 1gm10 I can run at 3400 rpm for short time then engine sounds like she's bogging out exhaust becomes dark with large oil patches does any one have any recommendations?
Thanks cal.