Black Oil

radarman

radarman

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Noticed today that my oil seems very black. Additionally when I first start the engine (old 10hp Bukh) black oil comes out of the exhaust intially then everything seems ok. Once started the engine seems to run ok. It still feels like it's got loads of power and doesn't seem to smoke.

I did notice that the oil level seemed to be quite high. Could this just be excess oil somehow gathering in the cylinder?
 
radarman said:
Noticed today that my oil seems very black. Additionally when I first start the engine (old 10hp Bukh) black oil comes out of the exhaust intially then everything seems ok. Once started the engine seems to run ok. It still feels like it's got loads of power and doesn't seem to smoke.

I did notice that the oil level seemed to be quite high. Could this just be excess oil somehow gathering in the cylinder?
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The increased oil level might be because the oil is sitting on top of water in the sump. A common way for water to enter these engines is when the water pump seals fail and water finds it's way along the pump shaft and through the chain case.

A clue is water being expelled from the tell-tale holes on the pump, unless they are blocked with paint or dirt.
 
If your oil level's high, it could be splashing up the sides of the bores past the rings and into the cylinders - causing excess drag and the problems you describe. As always, keep the level between the marks on the dipstick. There IS such a thing as too much..

I would also say if your oil is very black, it needs changing. Draining out and refilling with fresh oil is the best way to correct the level - and protecting the life of your engine.
 
Oil level too high is almost as damaging as too low, and can thoroughly mess an engine up. Diesel oil does go black as carbon (soot) is washed off the cylinder walls. This forms an increasingly effective grinding paste and increases wear on the engine specially the bearings - which you do not notice until it is too late a few seasons later! Thats why filter and oilchanges can not be missed in the service schedule.

The oil in in the exhaust is also almost certainly soot being washed through the exhaust, unless it is leaving an oil sheen on the water behind the boat. If water is in the sump it emulsifies the oil, which takes on a characteristic 'mayonnaise' appearance, evidenced on the dip stick.
 
Black oil-

If you had water in the oil, on running the engine it will quickly turn the oil white and creamy, so discount that one.
If you believe that the level is rising, oil is blacker than usual- does it 'feel' thinner, or smell of diesel? Could be a first sign of a faulty fuel injector, dripping fuel into the bore when the engine is stopped.
This will leave your exhaust oily on start up.
Even if the engine runs OK without excessive smoke it could be the beginning of a problem.
Other possibilty of high oil level is fuel contamination from the injection pump, or the diaphram in the fuel lift pump.
Or maybe it just had too much oil in to begin with?
Lots of possibilities, so I would start with an oil change, and get the oil level exact, then monitor over several hours of running.
 
have always found that the oil in the boat engine goes black incredibly quickly - my theory has been that with the pump out rather than drain out method (even with the superb vacuum pump thing that swmbo bought to reduce tempers when oil changing compared to traditional brass hand pump!) there is always a residue in the system of black oil that we couldn't get out and that residue - mixed with the lovely clean oil and the carbon deposits turns the new oil black very very quickly - by contrast in my caterham 7 when I drain the old oil it looks the same as when it goes in - mind you - the caterham does a lot less hours than the boat engine albeit at somewhat higher revs!

does everyones boat diesel engine oil go black almost straightaway?


ps out of interest (concern~) just went and checked the appearance of the oil in my company ford diesel - black as black can be - reassuring
 
PaulR said:
- my theory has been that with the pump out - by contrast in my caterham 7 when I drain the old oil it looks the same as when it goes in - mind you - the caterham does a lot less hours than the boat engine albeit at somewhat higher revs!

does everyones boat diesel engine oil go black almost straightaway?


ps out of interest (concern~) just went and checked the appearance of the oil in my company ford diesel - black as black can be - reassuring
Click to expand...

Didn't know they did a diesel Caterham!

Yes Oil goes black very quickly in old marine engines. I do notice that my VW and Merc diesel the oil stays golden for a lot longer. This is because these engines are built to much tighter tolerances and have much better combustion, so less soot.
 
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Yes, oil goes black immediately when refilled, volvo 2001 bout 13 yrs old. Always suspected it was because all old oil was not sucked out. Bought Pela Vacumn pump instead of brass one which made life much easier when removing old oil but didnt solve the black problem.
 
does everyones boat diesel engine oil go black almost straightaway?
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Mine certainly doesn't - 6 cylinder non-turbo Iveco. I'm surprised no-one has mentioned the contribution the low quality industrial/agricultural (red) diesel that UK boaters use makes to the discolouration of the lubricating oil. Our last two boats have been keep in mainland Europe and have been run exclusively on road quality white diesel. The oil in both has stayed relatively clean for the whole season (about 200 hours)
 
My Yanmar engine was bought in Holland about 10 years ago and has never been run on red diesel. I change the oil at 150 hour intervals, when it is always utterly black. I hope the man who designed the horizontal oil filter will spend his million years in purgatory changing these filters, getting black oil all over himself, the engine and the bilge.
 
parsifal said:
The increased oil level might be because the oil is sitting on top of water in the sump. A common way for water to enter these engines is when the water pump seals fail and water finds it's way along the pump shaft and through the chain case.

A clue is water being expelled from the tell-tale holes on the pump, unless they are blocked with paint or dirt.
Click to expand...

NO this is not right......If the oil was sitting on water leakage then the oil and water would be whipped into a cream emulsion once the engine was run and make this obvious.

If the oil is really black and been in a long time then either the engine was overfilled at some point or you have a leaky fuel pump which is allowing diesel to leak into the oil. If you wipe the dipstick and take a sniff of the wiper then if this is the case you will smell the diesel smell.

Sounds like it is time to change your oil and refill to the correct level and then monitor the level to see if it creeps up.
 
Oil not going black straight away

I've got a 1988 Thornycroft 50 hp based on a Ford and following a replacement oil cooler , (leaking water into the system, the mayonnaise one previously mentioned) asked the local enjos to "clean out all the old all and not just change it". Wow what a difference; I can't even get the new oil to go black even after 50 hours. I must ask them what they used to clean out the system because the "old donk" (that's what she's called) sounds even more like a sewing machine than ever. After a long hard day in the sun (Greece) however, we still get that aghast look from neighbouring boats when the shout goes out that "she's cooled down enough, so somebody shoot the donkey" and pass the cold beer.
 
NorthUp said:
If you had water in the oil, on running the engine it will quickly turn the oil white and creamy, so discount that one.
If you believe that the level is rising, oil is blacker than usual- does it 'feel' thinner, or smell of diesel? Could be a first sign of a faulty fuel injector, dripping fuel into the bore when the engine is stopped.
This will leave your exhaust oily on start up.
Even if the engine runs OK without excessive smoke it could be the beginning of a problem.
Other possibilty of high oil level is fuel contamination from the injection pump, or the diaphram in the fuel lift pump.
Or maybe it just had too much oil in to begin with?
Lots of possibilities, so I would start with an oil change, and get the oil level exact, then monitor over several hours of running.
Click to expand...

Can't improve on that advice! Was about to say the same meself....
 
Ta for all the replies folks.

I changed the oil yesterday so shall monitor it over the next few weeks and see how it goes.

I recon I probabily filled it to much the last time.

Did notice yesterday that I get lovely globules of oil coming out the exhaust when I rev up the engine. So I suspect the problem might be ring related.
 
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