H34 minor issues

Claude L.-Auger · Jan 9, 2013

splax said:
I spoke to a friend about the transmission fluid, and he recommended pressurizing the heat exchanger. His assumption being that the transmission is cooled and a tube leak allowed the transmission fluid to be pumped into the raw water side of the heat exchanger. Scary if true.

If you have a 3GM30 your transmission is probably model KM3-A (and it's really a reduction gear with a cone clutch) is cooled strictly with the little bit of oil that is contains ! There is no tube going to it and back and no coolant taken through it internally. Insert a clear plastic tube carefully all the way in and siphon off whatever oil if any is in there. Then refill with 0.3 liters of regular 10 W 30 as recommended by yanmar and you should be good to go.

Dan Johnson · Jan 9, 2013

SPLAX, Claude A, and others...

Here is a pic of the builder's plate on the aft end of the transmission on my Yanmar 3GM30F in my '83 H34. Note the oil viscosity and amount stated.

Claude L.-Auger · Jan 11, 2013

Dan Johnson said:
Here is a pic of the builder's plate on the aft end of the transmission on my Yanmar 3GM30F in my '83 H34. Note the oil viscosity and amount stated.

Hi Dan,
FWIW I too have a plate that says straight 30 grade and that is what I use. I was quoting from the Yanmar Shop Manual, page 10-2 of the Reduction gear chapter (Attached). Take a look at the 3rd line from the bottom ! Go figure what one is supposed to do ?

kloudie1 · Jan 11, 2013

I take the meaning of the real Yanmar shop manual (mine is the same) to say that you should use the same oil as in the engine. For me that is a 15-40 Shell Rotella T
The manual says 10-30, cc class. CC was the highest class at that time . Today the highest rating is around CJ-4 ..

Claude L.-Auger · Jan 11, 2013

Kloudie, I also use 15W40 Rotella t in the engine and will continue doing that. Because of the plate on the tranny I have used 30 weight. I change the oil in the tranny once a year. Perhaps I should switch to 15W40 and save the trouble of carrying 2 types. Since the multi-viscosity 15W40 has the same properties as a 40 at the higher temps (210F) when tested, it really wouldn't make any difference at the tranny's operating temp. It might even help with the 15 weight grade at the lower temperatures at start-up and during the first few minutes of operation.

Splax, unless your tranny is a Hurth, then ATF shouldn't be used. Don't know what manufacturer's manual you are refering to ? Yanmar is the manufacturer of that engine and includes Kanzaki in its Shop manual. It's your boat however so it's your decision. Hope everything works for you.

Claude L.-Auger · Jan 12, 2013

follow-up on oil in tranny

Kloudie, in spite of what I mentioned in the previous post, there is so very little oil in that tranny that after reading this from the Amsoil site I believe I'll stick to using 30 grade in the tranny and leave the 15W40 Rotella T in the engine:
"Drawbacks of Viscosity Improving additives
Multi-grade motor oils perform a great service not being too thick at cold startup to prevent engine wear by providing more instantaneous oil flow to critical engine parts. However, there is a draw back. These additives shear back in high heat or during high shear force operation and break down causing some sludging. What's worse is once the additive begins to be depleted the motor oil no long resists thinning so now you have a thinner motor oil at 210 degrees. Your 10W-30 motor oil can easily become a 10W-20 or even a SAE 10 (10W-10) motor oil.""
http://www.upmpg.com/tech_articles/motoroil_viscosity/

kloudie1 · Jan 12, 2013

Indeed, Claude.. The straight 30 will stay where it is in viscosity.. but I change mine more often than the 250 hours recommended ..

Richard Bryer · Jan 13, 2013

Those numbers look way high. Suggested for mine ( 3GM) is 16X11 for 3 blade, 16X13
for 2 blade. I have a 14X7 CS 3 blade on now, had that re-sized from 14X9 because of being over propped- couldn't reach proper rpms. Original was a 2 blade 15X12.

Claude L.-Auger · Jan 13, 2013

Richard Bryer said:
Those numbers look way high. Suggested for mine ( 3GM) is 16X11 for 3 blade, 16X13
for 2 blade. I have a 14X7 CS 3 blade on now, had that re-sized from 14X9 because of being over propped- couldn't reach proper rpms. Original was a 2 blade 15X12.

Indeed, and I have never seen a 34 with a 3GM30 running a prop at 17X12. When I bought mine it still had the original 2-blades 15X15 which I eventually replaced with a 3-blade 15X11. I am getting 3150 RPM at WOT and GPS shows 6.5 knots at 2600.

Dan Johnson · Jan 14, 2013

Claude A. & Splax...

Claude A, I have the same page in my "real" Yanmar shop manual. I can't find a pub # or date in the manual, but have supplement pages, pub # Y00R0902 revised Jan 1982.

I am more inclined to use what the oil the builder's plate recommends rather than the manual's spec. Over the years I have found errors that have crept into service manuals--some glaring, some not so. It is possible that the maual updates the builder spec, but I'd want to see some sort of confirmation.

Splax...I have the original 15x12 right hand two blade prop that can push the boat with a clean bottom to 7.2 Kn at 3,300 rpm on the tach. We all know that the Yanny panel tach isn't true, but I haven't used my laser tach to see the difference at WOT. I cruise at 2,700-2,800 RPM at 6.2 to 6.5 Kns.

Dan Johnson · Jan 14, 2013

Claude A. & Kloudie...

I'm inclined to believe that the 20/30 viscosity on the builder's plate is for straight weight oil. The 20 or 30 weight being selected based upon operating temp range. I don't interpret it to mean a mulit-viscosity oil--20W30 to be specific. This seems to be your viewpoint as well.

Claude L.-Auger · Jan 14, 2013

Dan Johnson said:
I'm inclined to believe that the 20/30 viscosity on the builder's plate is for straight weight oil. The 20 or 30 weight being selected based upon operating temp range. I don't interpret it to mean a mulit-viscosity oil--20W30 to be specific. This seems to be your viewpoint as well.

Thanks for the comments Dan,

this is also my viewpoint and I have been using and will continue to use 30 weight in the tranny. I was toying with the idea of using 15W40 but I don't want to take any chance as with no more than the little 0.3 liters of oil in there to cool it, it's likely that the tranny runs hotter than the engine on long runs.

As for the prop, my Yanmar tack runs 75 RPM short of laser tack at WOT so when I read 3150 on it, I'm really getting 3225 with my 15 X 11 3-blade prop. No smoke at all. So I'm happy. And I get around 6.5 on the GPS at 2600 (calm seas of course) which also make me happy. Would I prefer a folding prop ? Indeed, but I'm not prepared to spend that kind of money for the extra 1/2 a knot I might get !!!

Claude L.-Auger · Jan 15, 2013

splax said:
Hello,
Dan, thanks for your input. It sounds like you have a good situation.
I talked to my boat's PO yesterday and he told me he never checked the transmission oil. It just didn't come to his mind to do it. ??!!!! I will drain the ATF that I mistakenly put in the transmission and look for metal shavings. I don't know what I could do to fix a problem if there was one beyond replacing the transmission.

Splax, if I was in your shoes, I would drain the ATF and replace with good quality clean 30 Weight motor oil. I would then put the engine in neutral and turn the shaft by hand several times both clockwise and counterclockwise. That will turn the tranny as if you were sailing in neutral and should flush all the leftover ATF out, mixing it with the new oil. Then, drain that new oil and discard and refill with new oil to notch on dipstick (screwed in). You should be good to go in the Spring. If any damage was done the tranny will slip and not engage until you are revving higher. At that point you might have to have it rebuilt. Double-check this with a call to Mack Boring. Good luck.

Fast Ed · Jan 15, 2013

Instead of rubber bumpers, I mounted pieces of large dock line under the cockpit sets. Just twist 3 strand rope over the existing pan head screws.

H34 minor issues

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