Yanmar transmission chattering in reverse.

[Nemisis]

Tha Boat is a 1982 Goman, Express 30, with a Yanmar 2GM( 15).
So, it’s 42 years old.
In its lifetime I’ve had chattering problems 3 times before, and solved it by deglazing the clutches.
The last time I measured the wear, and reversted the more worn gear/ clutch so the worn one was on reverse.
So now 4 years later, the reverse is chattering.
I took it out and deglazed both, and reinstalled it.
The reverse still chatteres.
I think I’ve exceeded the wear limits.
I could try mixing the gears and clutch, but I suspect I’d just get the chattering in forward.
I’d happily buy a new clutch, but I’m terrified at Yanmar pricing ( a bent piece of wire, the dipstick is $90.)
I’m wondering if I could machine a wee bit off the hub portion of the clutch, to allow it to travel a bit more?
Any suggestions would be greatly appreciated!
Nemisis

[S/V Illusion]

Did you replace the damper plate? That cause that type noise more so than the clutch plate

[kenbo]

If its a KBW10 you can get a rebuilt one at https://www.bshmarine.com/ Also ASAP Supplies has clutch plates for the Hurth HBW 10, same as Kanzaki KBW 10.

[lockie]

2GM 's came with KM2A boxes.

[Jono as 2234]

You sure it's a 2gm? Mine is that age and it's a2qm. I'm told they are quite different. Maybe the gearboxes too

[Nemisis]

Originally Posted by lockie

2GM 's came with KM2A boxes.

Thanks for the info. So far in my research I hadn’t found that .
Nemisis

[Nemisis]

Anybody know of a replacement for the KM2A gear reducer on the Yanmar 2GM?
Or a source of jest parts?
Memisis

[lockie]

fwiw I'm pretty sure a KM2P will fit the 2GM, should you come across one.

[skipperpete]

Originally Posted by Nemisis

Tha Boat is a 1982 Goman, Express 30, with a Yanmar 2GM( 15).
So, it’s 42 years old.
In its lifetime I’ve had chattering problems 3 times before, and solved it by deglazing the clutches.
The last time I measured the wear, and reversted the more worn gear/ clutch so the worn one was on reverse.
So now 4 years later, the reverse is chattering.
I took it out and deglazed both, and reinstalled it.
The reverse still chatteres.
I think I’ve exceeded the wear limits.
I could try mixing the gears and clutch, but I suspect I’d just get the chattering in forward.
I’d happily buy a new clutch, but I’m terrified at Yanmar pricing ( a bent piece of wire, the dipstick is $90.)
I’m wondering if I could machine a wee bit off the hub portion of the clutch, to allow it to travel a bit more?
Any suggestions would be greatly appreciated!
Nemisis

It sounds like you already have a very good understanding of how your gearbox works ….and the cone clearance measurement method so I can’t add any useful advice other than to suggest that you might benefit from investigating the Yanmar spring loaded shift control link. There are a couple of pages in the service manual regarding the link (assuming you have one installed) and the lever adjustment but I reckon you’re up for a new cone (provided that the cups in the gears aren’t too badly worn and the rest of the gearbox is ok).
Has anyone on the forum ever renewed the grooves on the cone or skimmed five or ten thou out of the cone hub??
I’m interested to see how you get the chattering problem resolved.