Kanzaki trans for 3qm30 Yanmar 1978

[Dymaxion]

Kg-m is not a normal torque spec, it's usually N-m, likely a typo in the manual. Clean the nut/shaft threads with brake cleaner, apply blue loctite to the nut threads, a drop or two is enough, then torque as hard as you can with a regular 1/2" drive socket wrench. Or use an 18" breaker bar if you want more torque. If excess loctite runs down the splines it will make the flange hard to get off, but a propane torch will free it in a minute. If it comes loose prematurely repeat using red loctite. If that comes loose Devcon epoxy is a permanent bond.

[Wotname]

Originally Posted by Dymaxion

Kg-m is not a normal torque spec, it's usually N-m, likely a typo in the manual. ........

I guess you don't read many older Yanmar manuals then .

They regularly use Kg-m even if others don't.

I am however re-thinking the typo explanation although right now it still (?) seems the best explanation.

I hadn't realised it was a M33 sized nut.
If it is a typo, then it has been repeated elsewhere in the manual.

See below (from later on in the manual).

[Wotname]

I'm now thinking the manual is correct; going by this chart with suggests the following max torques for a M33 (course pitch) Zn plated bolt.

Grade 12.9 - 1984 ft-lbs
Grade 10.9 - 1653 ft-lbs
Grade 8.8 - 1176 ft-lbs

This suggests the manual is correct!

Torque Tightening Values for Structural Steel Bolts - Chapman Steelwork Fabrication Ltd

[skipperpete]

Originally Posted by Wotname

FWIW, the 2QM20 Kanzaki transmission (KBW-10) uses the same special tool does the 3QM30 KH-18 transmission and the torque figure as per the manual is 9.5 kg m (68.7 ft lbs) so something seems to be incorrect somewhere

Hi Wotname,
The nut on the KBW10 is different in the way it’s locked to the output shaft, there is a shallow keyway in the shaft threads and the nut has a raised flange. When the nut is tight, that metal flange is indeed staked into the keyway hence the cold chisel in the manual pics doing the staking.
On the KH18 there is no such arrangement to lock up the nut.
Definitely agreed that you could cut down a stock machine nut but there isn’t enough room for a hex nut and socket in the coupling bore so the original slots would have to be replicated. I slavishly follow torque specs but putting 100kg into a meter long bar seems suspect and I probably get 50-60 kg on the bar if the transmission is in the boat and 80-90 kg on the workshop floor. I use loctite on this gearbox only and rarely on anything else.
We used slogging wrenches on cylinder head nuts but only to achieve a particular amount of specified rotation in degrees or flats so I can’t see how Yanmar expects us to quantify or translate bashing away with a lump hammer on their expensive slogging spanner to achieve an accurate torque on the gearbox nut.
We’re all in isolation/social distancing here so the forum can expect a few rambling incoherent posts from me indoors🤢

[Wotname]

Originally Posted by skipperpete

Hi Wotname,
The nut on the KBW10 is different in the way it’s locked to the output shaft, there is a shallow keyway in the shaft threads and the nut has a raised flange. When the nut is tight, that metal flange is indeed staked into the keyway hence the cold chisel in the manual pics doing the staking.
On the KH18 there is no such arrangement to lock up the nut. ............

We’re all in isolation/social distancing here so the forum can expect a few rambling incoherent posts from me indoors🤢

Thanks Skipperpete. I also now realise the KBW10 uses a M24 nut so that explains the difference in torque figures between the two nuts. I don't know if the outer dimensions are the same or not between the two and about now, I have stopped caring .

FWIW, I have never needed a reason to explain my rambling incoherent posts.