2003 Yanmar, 765 hours - milky oil, overheating, evacuating coolant - SailNet Community
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post #1 of 3 Old 05-10-2010 Thread Starter
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2003 Yanmar, 765 hours - milky oil, overheating, evacuating coolant

Hello everyone,

My relatively new Yanmar 4JH3E was unused for 3 years and has just been put back into service and has a problem: milky oil and overheating.

Before I started the engine the first time, I changed the raw-water impeller, the radiator cap, the thermostat and the pump/alternator drive belt. All the old parts were in good shape upon removal. Basic maintenance is the limit of my knowledge and ability - but I've always been good about doing it on a timely basis.

After launch, the engine overheated. Part of the overheating was evacuation of coolant: about a quart (of a total capacity of about 7 quarts) got pushed out of the engine and then the overheating happens quickly.

There is liquid in the oil - very milky. I've changed it each time as I've re-tested the engine and it gets milky again. It takes 20-40 minutes before the engine overheats (the gauge spikes to max in just a few seconds). The engine is now very hard-starting: you turn the key and there is a long pause as the starter tries to turn the engine and takes a few seconds to overcome the engines resistance to wanting to turn.

Any ideas of what the most likely problem is?
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post #2 of 3 Old 05-10-2010
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Sounds like a head gasket... the starting resistance is likely liquid in the cylinder(s), which may be leaking past rings into the crankcase - hence the milky oil.

It needs proper attention ASAP.


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post #3 of 3 Old 05-10-2010
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Here is your second opinion for a head gasket. - you hope!

Have a compression test done.
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