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Yanmar Gear Oil

Aug 3, 2014
65
Beneteau 343 San Francisco Bay
Having spent hours trying to find out the real skinny on gearbox oil, I found an online Yanmar manual that is much more complete and detailed than the one that came with my engine. Link as follows:
http://www.yanmar.no/theme/yanmarpo...eration-manual/YM-OM/0AYMM-EN0023_English.pdf
Specifically, one is to use MARINE gear oil, API CD or higher, KM2P-1 (S), (G), or (GG), SAE 20 or 30. Don't bother looking at the automotive store, as I checked several.
On my SD20 gearbox, attached to the 3YM30 engine, the gear oil is checked without screwing the dipstick in; the high mark is just above the base of the dipstick, and the low mark is essentially the base of the dipstick.
BTW, this manual covers several of the 3Y- - engines.
 
Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
Nice to know SOMEbody gets the manuals and reads them.
 
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May 24, 2004
6,799
CC 30 South Florida
Good luck finding that lubricant. Was looking at a cross reference lubricant guide and out of 32 different brands of lubricants (Texaco, Shell, Conoco, Amsoil.....)not a single one labeled a product as Marine Gear Oil. They had cutting oil, tractor oil, automotive oils, Paper machine oil, compressor oil and even Aviation motor oil SAE 60 but none with a Marine designation. I would consider that the job of a motor oil would exceed by far the demands of the oil for a transmission. Pick a quality single SAE 30W motor oil at your automotive store and it should work fine.
 
Oct 29, 2005
2,187
Hunter Marine 326 303 Singapore
I use same Shell 15W40 cd grade for my 2gm20f and for gearbox km2-p.
 
Nov 6, 2006
9,226
Hunter 34 Mandeville Louisiana
I believe that you may be mis-interpreting semantics in the translation from Japanese.. Pretty sure what they are saying is that for YOUR "marine gear" (transmission) the correct oil is 30 wt engine oil, the only oils listed with the API certifying tests. No "gear oil" is rated by API.
 
Jun 6, 2006
6,991
currently boatless wishing Harrington Harbor North, MD
There is a very good reason why you cannot find the API CD (anything) oil. The standard is obsolete!!! They don't make it because there is a better one available.
http://www.api.org/products-and-ser...ories-and-documents/oil-categories#tab_diesel
The link would seem to indicate that the current best API for engines is CJ-4. BTW API CD is a MOTOR oil not a GEAR oil. This makes sense when you understand the third para in this link
https://www.lubrizol.com/DrivelineAdditives/AutomotiveGearOilAdditives/default.html
API is great and all but use your best judgment.
With all that said: GEARS are different from MOTORS. Gears need high pressure and low traction type oils. Unless you sail in the higher latitudes or in the winter (the horror!) your low temp performance is not that important so you don't need a wide viscosity (weight) oil.
This is a good reference for the different types of gear oils and what you would use them for. Note that "GL" is gear lub, and "MT" is manual transmission and these are API numbers. I'm thinking that most of us would be needing SAE J2360. the description of the standard is here:
http://standards.sae.org/j2360_201204/
and looky there is some of this stuff available. Thinking the 75-90 weight is sufficient unless you sail in Dubai
https://mobildelvac.com/en/ancillary-products/mobil-delvac-synthetic-gear-oil
The confusion is all about the "or better" part.
 
Jun 21, 2004
1,884
Beneteau 343 Slidell, LA
JM,
On my 343, with the Yanmar 3YM30, the identification plate attached to the transmission specifies 30wt oil. I just use a quality motor oil. And yes, when checking the fluid level, I don't screw the dipstick into the transmission--just let the cap rest on the fill hole.
 
Feb 21, 2008
358
Hunter 33 Metedeconk River
Just slightly off topic; any tricks for reading the dipstick? I once heard that you could paint the bottom of the stick with white auto enamel to make it easier, but I hesitate to put anything in the gear box that don't belong.
 

Rick D

.
Jun 14, 2008
7,005
Hunter Legend 40.5 Shoreline Marina Long Beach CA
Just slightly off topic; any tricks for reading the dipstick? I once heard that you could paint the bottom of the stick with white auto enamel to make it easier, but I hesitate to put anything in the gear box that don't belong.
 

Rick D

.
Jun 14, 2008
7,005
Hunter Legend 40.5 Shoreline Marina Long Beach CA
I scuffed it up with coarse wet/dry sandpaper.
 
Jun 21, 2004
1,884
Beneteau 343 Slidell, LA
You can also hold the dipstick against a clean paper towel to see where the oil level is on the stick. Definitely hard to see the oil level when only looking at the stick.
 
Sep 15, 2009
6,242
S2 9.2a Fairhope Al
You can also hold the dipstick against a clean paper towel to see where the oil level is on the stick. Definitely hard to see the oil level when only looking at the stick.
i totally agree with this ...i have often wondered why they didn't knurl that stick to begin with
 
Jun 6, 2006
6,991
currently boatless wishing Harrington Harbor North, MD
I'm telling you guys that MOTOR oil does not have the high pressure lubricants that are needed for gearboxes. The only place I've ever seen motor oil use in a gear box is motorcycles which share crankcase and gearbox space.
 
Nov 22, 2011
981
Ericson 26-2 San Pedro, CA
I'm telling you guys that MOTOR oil does not have the high pressure lubricants that are needed for gearboxes. The only place I've ever seen motor oil use in a gear box is motorcycles which share crankcase and gearbox space.
And yet, for at least *some* of the Yanmar (Kanzaki) transmissions, both the plate on the transmission and the printed documentation clearly specify to use the same oil as in the engine, which is 30 wt. oil. (My transmission is a KM2-A.)
 
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Jun 21, 2004
1,884
Beneteau 343 Slidell, LA
Maybe there is a gear oil that would be more suitable for the transmission; however, I would not use a lubricant that has a viscosity 3X that recommended by the manufacturer.
 
Nov 22, 2011
981
Ericson 26-2 San Pedro, CA
Maybe there is a gear oil that would be more suitable for the transmission; however, I would not use a lubricant that has a viscosity 3X that recommended by the manufacturer.
From the "Yanmar GM-HM Workshop Manual":
"Transmission models KM2A, KM2C, KM2P, KM3A and KM3P
The recommended transmission oil is an engine oil that meets API classification CC. The recommended viscosity is SAE 10W-30. Change the transmission oil after every 250 hours of operation."
The plate on my KM2A specifies simply SAE 30, so I just go with a straight 30 wt., as I do for the engine. But the point is, the transmissions shown above just use engine oil. Granting that my transmission works just fine after 26 years without a rebuild, I'd have to think Yanmar knows what they are talking about.
The same manual goes on to specify ATF for transmission models KBW10D and KBW10E.
 
Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
Bill, I think you need to quote your source, rather that to just say"I'm teeling you guys" in contrast to every answer posted. I don't know where you come up with "high pressure" in transmission. Mine takes .3 litre . The lowestest gears pick up the oil on thier teeth and pass it onward as the teeth mesh with other gears.
 
Dec 25, 2000
5,049
Hunter Passage 42 Shelter Bay, WA
FWIW, our Kanzaki transmission takes ATF according to the plate that was placed by the manufacturer on the bell housing that connects to the 4JH2-TE engine. Our owner's manual says to use engine oil, but the service manual says ATF. So I deferred to the manufacturer's identification plate.
 
Jun 6, 2006
6,991
currently boatless wishing Harrington Harbor North, MD
Ron20324, I'm pretty sure you will agree that sliding pistons and flat bearings are a different kind of friction than the sliding of gear tooth on gear tooth. My reference is an old motorcycle racing guide that I read back in the 70s. Don't remember the name but let me put it this way, why do you think they make gear oil (ATF is gear oil BTW) and put it in every car made? most of the manufacturers that recommend motor oil in gear boxes are from the orient and deal with small (read less than 100HP) engines. I have no doubt that motor oil will work in transmissions of this sort and you will probably have no problems due to the low loading. however, I plan on having the boat for a long time (still boats in the water from the 60s, seen many 60s eara cars lately) so I'd recommend you use oil that will give the longest life. There is also the prudent sailor line since the iron spinnaker is a key safety item for most sailors.
your boat, your decision but go in with eyes open.