Gear Box Oil

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Murray16764

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Oct 16, 2007
52
Beneteau 352 Toronto
I was planning on changing my gear box oil on my Ben 352. The boat has a Yanmar 3GM30 with the standard gear box. The marine supply store advised to use normal motor oil in the box - 10W30, for example. No special oil required. Is that correct? I would think the gear box is a lot less technical than a engine. What do you guys think?

Murray
 
Tim R.

Tim R.

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May 27, 2004
3,626
Caliber 40 Long Range Cruiser Portland, Maine
Check with the manufacturer. My Hurth transmission only takes ATF.
 
Chuckbear

Chuckbear

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Jan 3, 2009
821
Marine Trader 34 Where Ever I am
If you have the standard gearbox that comes on the Yanmar engines then you will use the same oil you use in the engine. But it is a good idea to check first. Call your local Yanmar service center. Chuck
 
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Barnacle Bill

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Jun 9, 2008
1,817
- -- -Bayfield
I believe the lubricating oil for a Yanmar 3GM is Dextron-ATF. Refer to your owner's manual for the proper lube. Do not take some guy's word for it a the store unless they are qualified and know or can refer to Yanmar specs. Usually the engine oil for the crankcase is NOT a multi grade oil either. 30 weight is standard, but check your owner's manual. That is what it is there for.
 
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Murray16764

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Oct 16, 2007
52
Beneteau 352 Toronto
Yes, I'll check the manual. The advise I recieved was from a Yanmar service dealer. It sounds right, but I will double check it. Thanks for your help.
 
SamLust

SamLust

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Jan 2, 2008
547
Hunter 33 (Cherubini design Forked River, Barnegat Bay, NJ
The lubricant for Yanmar gears from the period in question is straight 30 weight. I believe they want non-detergent, which is non heavy duty. Multi-grade or any sort of ATF are wrong.
 
Don S/V ILLusion

Don S/V ILLusion

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Sep 25, 2008
7,599
Alden 50 Sarasota, Florida
Murray16764 said:
Yes, I'll check the manual. The advise I recieved was from a Yanmar service dealer. It sounds right, but I will double check it. Thanks for your help.
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Murray
You might also do well to verify what transmission model you have as certain engines, incl yours, can also use different transmissions.
The link below, from Yanmar, will confirm what fluid should be used:

http://www.yanmarhelp.com/i_box2.htm
 
zeehag

zeehag

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Mar 26, 2009
3,198
1976 formosa 41 yankee clipper santa barbara. ca.(not there)
my yanmar dealer says 30 wt oil is used in gearbox--gooood luck.....
 
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Steve Dion

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Dec 2, 1999
15,184
Hunter Vision-36 Rio Vista, CA.
GM engine used 30wt (don't know if multi-grade is adequate), but I would always check your manual for your exact transmission.
 
sailaway78

sailaway78

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May 11, 2005
3,431
Seidelman S37 Slidell, La.
Tranny oil

My manual for a 3GMD says ATF. Just looked, as I need to change mine also. Have been told by several different supposedly knowledgable people, to use what is in it now. Either 30W or ATF.
 
Chuckbear

Chuckbear

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Jan 3, 2009
821
Marine Trader 34 Where Ever I am
Nice N Easy said:
My manual for a 3GMD says ATF. Just looked, as I need to change mine also. Have been told by several different supposedly knowledgable people, to use what is in it now. Either 30W or ATF.
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That is a good point. What is in it now. If it is red it is transmission fluid, if brown it is oil, so use your engine oil. Chuck
 
Stu Jackson

Stu Jackson

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Feb 26, 2004
23,139
Catalina 34 224 Maple Bay, BC, Canada
Gotta be VERY careful here, folks

different engine trabnsmissions require different fluids, yup, we all know that, BUT:

old red transmission oil can look brown if left too long without changing

30W and ATF are COMPLETELY different things

color doesn't matter

it's what's on the label on the container AND what your engine's transmission REQUIRES.

And, for those with engines and other transmissions than the Yanmars, the Unviersals, for instance, require tranmission fluid, NOT engine oil, and they can take either Ford or Dexron. Dexron started out as that, then moved up to I, II, and now III, if not higher numbers (Roman numerlas, just like the Super Bowl!!!) Don't mix the Ford with Dexron.
 
D

Deadline2

Two minds

The confusion stems from Yanmar, which gives conflicting advice of ATV vs. 30w. I rather like Nice n' Easy's logic, which is to replace whatever is in there.

If as the other fellow suggests that there's a big diff between the two, how come Yanmar can't get the distinction?
 
Stu Jackson

Stu Jackson

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Feb 26, 2004
23,139
Catalina 34 224 Maple Bay, BC, Canada
Deadline2 said:
If as the other fellow suggests that there's a big diff between the two, how come Yanmar can't get the distinction?
Click to expand
Perhaps because Yanmar doesn't make the transmissions. (I personally don't know, 'cuz we don't have a Yanmar engine.)

That's why I suggested that it is not the engine, it is the transmission.

For instance, Universal doesn't make transmissions, they distribute tractor engines made by Kubota, and boats with those engines use Hurth transmissions, which require ATF, not oil.

That's all...

And why not just reread Don's reply #7, he got it right!
 
kloudie1

kloudie1

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Nov 6, 2006
10,152
Hunter 34 Mandeville Louisiana
Interesting notes regarding transmission oils..
ATF is sort of like 10W30 in terms of viscosity.. they have viscosity specifications that are very close.. The thing about ATF is that it has “friction modifiers” in it which makes it not as slippery as motor oil, in some areas of contact and same slippery in other points of contact.. In an automatic transmission, you want the gears and bearings to be lubricated but you do not want the clutches to slip.. The friction modifiers in the ATF allow these seemingly opposite needs to happen.. normal 10W 30 crankcase oil in an automatic transmission would let the clutches slip and it would overheat fairly quickly. In a regular gearbox like what I have behind my 3GMF, the manufacturer calls for “crankcase oil”.. If ATF were to be put in, it would not hurt anything.. there would be plenty lubricity to keep the bearings and gear contact faces happy.. In fact it would make the cone clutches work a little better since the friction modifiers are made to do that.. If ya have a hydraulic gearbox like would be on a Yanmar 3HMF, ATF would be required and normal crankcase oil would probably let the clutch disks slip, which would overheat the transmission.... Soooo.. In a nutshell, you may safely use ATF in all transmissions (talking small marine transmissions up to about 100 hp, not talking bevel gear oil) but if you have a transmission that has multi-disk face clutches, ATF is the ONLY thing that should be used.. but try to stay close to the manufacturers recommendation for your particular transmission..
 
kloudie1

kloudie1

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Nov 6, 2006
10,152
Hunter 34 Mandeville Louisiana
There are two basic different types of small marine transmissions.. requiring two different oils.. One has multi-disk face clutches. The other has cone clutches for transferring the drive torque between the transmission shafts.. The clutches are very different .. The cone clutch may use ATF or motor oil.. The face clutch must use ATF only..
 
Stu Jackson

Stu Jackson

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Feb 26, 2004
23,139
Catalina 34 224 Maple Bay, BC, Canada
Don S/V ILLusion said:
Steve.
Great minds think alike... I tried that in post #7 of this thread ... Makes you wonder - why bother...
Click to expand
I agree, and tried to get them to go to your #7 earlier.

Seems if ya don't give 'em a link they won't go there, and even if you do....:doh:

I think we keep trying because we have quite a nice community here, and eventually those guys will pass it on, just like we do out on the water. :)

Oh, and I keep learnin' somethin' all the time.
 
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