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mbsl98 10-15-2010 11:18 AM

Yanmar 3GMD transmission oil confusion in manuals
Sorry to raise a question that has been around before, but I can't find a definitive answer. My original paper manual for my 3GMD (which covers the 1, 2 and 3 GM's and 3HM) has a separate note specifically for the 3GMD engine alone, that the oil in the tranny is different from the oil used in the engine and a warning to use the proper oil, and refers me to a chart on another page. That chart shows the engine oil and tranny oil to be the same for the 1, 2 and 3GM, while the 3HM uses Dexron. I also have a downloaded version of the 3GMD manual, and it has the same note, but no cross reference or any reference at all to the specific oil to be used in the tranny. In the downloaded version, the note is explicit in saying that the 3GMD and 3HM use different tranny oil than the engine, although there is no oil spec that i can find in that manual.

Does anyone have a source for a definitive answer on the tranny oil (engine oil or Dexron)?

Also, interesting definition of how to measure the tranny oil level in both versions of the manual: ".....check with screwing the dipstick". I understand that the common consensus is that this means to unscrew the dipstick and leave it resting on the top of the threads, but hard to get that from the written words :)

JohnRPollard 10-15-2010 12:49 PM

We have a 3GM30F in our boat. I'm not familiar with a "3GMD" variant. What does the "D" signify?

But I do know about that discrepancy. The manuals contradict themselves. I was told by a mechanic that I trust to use straight 30W motor oil in our Kanzaki transmission. We check the level with the dipstick unscrewed.

mbsl98 10-15-2010 03:02 PM

Thanks, John. The 3GMD was the first version of what became the 3GM30. It was produced 1981-1983 or so, at which point it became the 3GM30. The D is rated at 20 hp sustained running at 3400, with 22.5hp at 3600 for one hour max, while the 30 version ups the rating to 24 hp at 3400 sustained and 27 at 3600. Other than whatever they did to up the ratings, it appears to be almost exactly the same engine and transmission. My concern is that both manuals make a specific point of saying that the 3GM uses a different tranny fluid than engine oil. I believe that my new to me 1985 Marshall 22 catboat has engine oil in the tranny, based on its light golden color, and the concern is that it seems to be contra to what the book calls for, although it runs just great. Based on the year of the boat, I assumed the motor was a 3GM30, until I found a plate on it saying it is a 3GMD. It is certainly more than enough power for a 22' sailboat :) , easily pushes it well past hull speed of 6.1 to a bit over 7 knots, and makes it feel sort of like a motorboat as the bow lifts. Not an efficient way to cruise, but fun now and then.

JohnRPollard 10-15-2010 04:07 PM

Oh, that's an interesting bit of Yanmar history. Sound like the "D" is plenty of engine for your boat, too. I love those Marshall catboats, by the way.

Anyway, like I said, our manual has contradictory info about the tranny oil, too. In one place it says to use ATF, in another it says to use the same weight/type as the engine oil. When we got the boat, I asked a trusted mechanic and he said that info about the ATF is incorrect and only applies to the 3HM35.

Faster 10-15-2010 04:41 PM

Crazy that a contradiction like that got by the proof readers and the users.. do you know if any correction/errata document was ever issued?

Many gears DO use ATF so I'd never have questioned it.....

RichH 10-15-2010 04:42 PM

On most transmissions used by Yanmar, the type of 'oil' is usually stamped into the transmission ID plate (along with Mod. and Serial #'s) ... and may be different from the published 'manuals'.

mbsl98 10-17-2010 05:55 PM

Thanks for the updates. I have not found any reference to any tech updates, and the on-line manual I downloaded was from Yanmar so I would have expected any corrections to be in that - it is not the same as the original manual (in several languages on each page) so they could have easily changed the spec if they wanted to. I have not found the traqnny ID plate yet - it has been painted over along with the prior owner's regular touch up painting of the engine with Yanmar grey paint - nice thick stuff that seems to fill in engraved info nicely :( I tend to think that the engine oil is likely correct, since the prior mechanic used it in mine (I'm pretty sure from color) and lots of people on these forums seem to think it is right also. I want to change it just for routine maintenance over the lay-up, but I may wait a little longer to see if any more info surfaces.

casey1999 10-18-2010 12:26 PM

yanmar 3gmd
I have the yanmar 3gmD. I think the D stands for direct sea water cooling where a 3gmF stands for fresh water cooling. I was also confused by the different oil spec in the manuals. On my transmission I changed oil using a 40 WT as this is what a Yanmar dealer told me to use. Since then I did find the name plate on the Kanzaki (V drive transmission) that says use 15-30 wt. I have not changed the trans oil since seeing this new information and have run 50 hours without problems- maybe I should change to the 15-30 wt. I agree the oil specs are confusing- maybe I should contact Yanmar factory and see what they say.

mbsl98 10-25-2010 10:39 AM

Just a quick update. I found the ID plate on the Kz transmission with my 3GMD. As best as I can read it upside down and through the touch up paint, it calls for use of .3 liters of 20/30 weight oil. Since there has never been a multi-weight 20/30 that I know of, I assume that this means it should have either 20 or 30 weight engine oil. I understand that Yanmar has updated the original engine oil spec form the old 30/40 to a multi-weight 15-40, so i don't know if there is an update to the tranny oil spec as well. In any case, it is clear that the manual references to ATF are not correct.

casey1999 10-25-2010 12:03 PM

Just curious what the ATF fluid would do to the transmission- would it damage it?

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