Black transmission oil

Ralph Johnstone · Apr 21, 2014

Sure you weren't taking oil from the engine

We know you weren't so what to do ? ? ?

The fact that the oil has been in there since 2010 is not the best thing for it as I believe maint. specs call for it to be changed with each engine oil change. Maybe someone here with your engine can confirm or correct.

I hope you still have the old oil as you should send it off to an appropriate lab and have it analysed. They will be able to tell you what is causing the colour and you can deal with it. If the oil has been disposed of, take a sample of the new oil in your transmission (which will contain some of the old oil) and have it analysed. It will at least give you some idea of what's in there.

After that, I still think oil analysis every 100 hours (or the labs recommendation) would be in order. It may be something serious or not. If not serious, you don't want to be tearing out your transmission. If serious, any chance of taking on a second or third job :cry:?

Forrest15112 · Apr 21, 2014

On a car, black transmission fluid means it's burned. You could just change it a few times to run the burned stuff out and watch closely, or better yet, have the transmission looked at by someone who knows what to look for.

Chris Patterson · Apr 21, 2014

Send the oil off and analyze it. Keep very close watch over your time schedules, etc, and then dump the oil again after X hours, (not a thousand, not even close), and sample the next batch. A benchmark will help, and heavy contaminants in the second pull will be a better number. Truth is, a mechanic needs to be very, very careful of every thing he uses in this extraction process, so as not to clutter the field.

(Chances are, the oil has been hot for quite some time, thereby 'burning' it because the gearbox has clutches in it. Despite what Yanmar 'says', if the oil is coming back tar black before its recommended service interval, I would just change it more often. I would hate to think I trashed a five grand gearbox over twenty bucks worth of oil).

Bad Obsession · Apr 21, 2014

I hate to sound like a butt, but you sure that you didn't add a 0 to that number.

I change my transmission fluid every year in the maintenance. 50-100 hours?

1000 hours sounds a bit long to have that in there.

Chris Patterson · Apr 21, 2014

Personally, there is no way I would leave oil in any marine gearbox for 1000 hours, I don't care if Jesus said it..

Stu Jackson · Apr 21, 2014

2010 to 2104, four years, maybe 100 hours per year on the engine = 400 hours.

1,000 hours means he used the engine 250 hours per year, which, while highly unlikely, could well be the case.

Since it's only the beginning of the 2014 season, the numbers are worse/better using only 3 years, right?

Chris is right, one oil analysis can only tell you if you have metal shavings in the oil, it takes to two tango, oops, to make any analysis worthwhile, 'cuz they compare sample #1 to sample #2.

capta · Apr 21, 2014

Is this a hydraulic trany or gear? If hydraulic, the oil should be red unless you are using engine oil instead of ATF, which is acceptable, though rare outside the commercial vessel industry. If it's black, it could be an indication that the discs (clutch plates) are wearing excessively.
If it's a gear trany, then it's probably been too long since the oil was changed and I would probably pour some fresh oil through it before refilling, to clean it a bit.

Jake N Eggs · Apr 21, 2014

For what it's worth, wearing aluminum components will turn oil black. There would be no burned oil odor. As stated above, oil analysis would show a high Al content.

kloudie1 · Apr 21, 2014

KM3 is a cone clutch transmission and not a disk clutch transmission. It is supposed to use a good grade of mineral oil which the manual says to use the same as the engine oil. Most folks use a straight grade 30 wt engine oil because the multi grade engine oils are not as good as straight grade for gearbox use. The black may be the result of sailing with the transmission in forward? (assuming no folding or feathering prop). This might slip the cone clutches and result in some black oil. The drive cone is made of aluminum-bronze so any corrosion will color the oil black. Any tiny amount of seawater in the box might do that .. Rolling element bearings in failure mode will color the oil black as well, but you should be able to feel that as a "crunchy-ness" if you were to put it in forward, release the compression, and have someone slowly turn the engine over while you feel the case and output shaft .. No "crunchy" is good. Pass some of the black oil through a coffee filter .. if there are lots of small metal shards or flakes that are visible, you probably have a failure in progress.. If it is just black and no metal flakes, change the oil and change it again in 50 or so hours to keep tabs on what is going on. Don't put automatic transmission oil in a KM3.

Gunni · Apr 21, 2014

Oil changes are not exclusively engine hours-based. They are hours OR calendar. In your case you should be changing your transmission oil every year because you don't put many hours on the engine. That oil takes a friction beating. FYI, it should come out pretty much clear. You have a problem.

capta · Apr 21, 2014

kloudie1 said:
KM3 is a cone clutch transmission and not a disk clutch transmission. It is supposed to use a good grade of mineral oil which the manual says to use the same as the engine oil. Most folks use a straight grade 30 wt engine oil because the multi grade engine oils are not as good as straight grade for gearbox use. The black may be the result of sailing with the transmission in forward? (assuming no folding or feathering prop). This might slip the cone clutches and result in some black oil. The drive cone is made of aluminum-bronze so any corrosion will color the oil black. Any tiny amount of seawater in the box might do that .. Rolling element bearings in failure mode will color the oil black as well, but you should be able to feel that as a "crunchy-ness" if you were to put it in forward, release the compression, and have someone slowly turn the engine over while you feel the case and output shaft .. No "crunchy" is good. Pass some of the black oil through a coffee filter .. if there are lots of small metal shards or flakes that are visible, you probably have a failure in progress.. If it is just black and no metal flakes, change the oil and change it again in 50 or so hours to keep tabs on what is going on. Don't put automatic transmission oil in a KM3.

Thanks for that post. I am unfamiliar with that trany so thanks for all the good info.

Benny17441 · Apr 21, 2014

The shop manual for the Kanzaki recommends oil change at 250 hours. That does not mean that we get a pass from periodically checking the oil level and condition. I know we are prone to interpret transmission hours as those when the engine is running, but realize that the transmission is operating even when it is just freewheeling under sail. For that reason the oil should be changed more frequently than what the engine's hour meter may indicate. Keep a rough running tally of the hours the boat is underway and check the oil periodically. What oil was being used? The Kanzaki requires motor oil and not ATF. Have seen where some have incorrectly used ATF and it does tend to get dark.

Lee Coller · Apr 21, 2014

Yanmars should be left in neutral while sailing: http://forums.sbo.sailboatowners.com/showthread.php?t=116625&#post700362

Bill Roosa · Apr 21, 2014

What does the oil smell like? Also, flush the tranny with a cup or so of new oil and put it in a glass jar. Let it sit for a few hours and check for sediment. You can then pour off the oil on top and feel the sediment.
Engine hours and tranny hours are NOT the same. Tranny hours would also include all that time in neutral while sailing and the prop is spinning. Yanmar recommends this BTW. I would not be worried with the 1000 tranny hours between changes as the oil is not seeing combustion products.