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Old 02-09-2014, 07:21   #1
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Gray Smoke

motor sailing at at night and altenator belt broke and engine got hot .
Changed belt next morning and engine ran fine and carried a load.
I had the boat hauled for thru hull fittings and on the way back the delivery person noticed Grey smoke from exhaust stopped after a while .
I do plan on having a diesel mechanic check it out bbut just curious if anyone else has experienced this or have any answers. My first thought is either cracked head or blown head gasket .
Almost no loss of water and does not use any oil.
I know white smoke is water and black smoke is oil.
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Old 02-09-2014, 07:52   #2
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Re: Gray smoke

Not a mechanic but I believe if you had a blown head gasket you would notice a drop in coolant/water levels since fluid would be leaking into the engine.

What type of engine do you have?
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Old 02-09-2014, 09:15   #3
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Re: Gray smoke

Grey smoke is generally not possible on a diesel engine. You need to decide if it is bluish or blackish.

Bluish is burning oil.
Blackish is overload from restriction or from prop wrap or fouling of the hull.

I would monitor smoke, monitor fluid levels and hope for the best.

Actually if it was my engine I would stick my hand in front of the exhaust and wait till my hand got dirty and then I would smell it and feel it.

I also might look in the freshwater system for signs of oiliness and or bubbles at temperature.

I would also drain some oil and look for milkiness or water.

But if I didn't find anything and the smoke was pretty light or intermittent I would probably motor on with a careful watch and hope for the best.
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Old 02-09-2014, 09:49   #4
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Re: Gray Smoke

Pull the dipstick and check for milkiness in the oil. Check the heat exchanger for presence of oil. Ex-Calif had a good suggestion re putting hand in exhaust stream. But he didn't tell you what each smell might mean. I wonder - if it smelled like my dog's farts, Ex-Calif, what would that signify?
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Old 02-09-2014, 16:33   #5
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Re: Gray Smoke

The question is what if it doesn't smell like dog farts -

Describing what to look and smell for is almost impossible. So that's what "I" would do.

I would be trying to assess if it is normal oily (as a diesel would be) or extra oily as a diesel that is burning oil would be. Or if it was more steam/vapor.

If he has damaged the headgasket or something there should be fluid loss somewhere...
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Old 02-09-2014, 17:07   #6
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Re: Gray Smoke

Quote:
Originally Posted by crazyoldboatguy View Post
I wonder - if it smelled like my dog's farts, Ex-Calif, what would that signify?
It means you got your hand by your dog's butt instead of the boat's
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Old 02-09-2014, 17:25   #7
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Re: Gray Smoke

Fluid loss is the key. You can be losing fluid without anything coming out of the exhaust, altho that is not as likely. Lots of steamy looking stuff coming out of the exhaust is not a good sign. I haven't seen that happen on a diesel so can't be sure what the plume would look like. Unless it looks like my dog's...
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Old 02-09-2014, 18:24   #8
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Re: Gray Smoke

Gray smoke is generally unburnt fuel, It can be caused by leaking / fouled injector, timing off on the IP, leaking oil seal on a turbo (if one fitted), miss adjusted valves or poor fuel. Can also be caused by broken rings, but lets not go there.
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Old 02-09-2014, 18:49   #9
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Re: Gray Smoke

My engine went from great to non starting after a grey smoke incident in six hours. Broken head gasket was the cause sprayed water onto cylinder head and cracked it.
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