Scuffing a Yanmar YSE 12 clutch?

[Will10MNT]

I lost foward power from the transmission some time ago, its a 1974 yanmar yse 12, and took apart the gear box to try and 'deglaze' the foward clutch plate. Ive finally got the thing apart after a lot of confusion, but now im not positively sure what part here I should be cleaning with what, sanding, or adding any fine grinding paste to, or what damage is really present on any of the plates. Any help is greatly appreciated, happy new years all.

[Wotname]

If you don't have the YSE service manual, PM me with an email address and I can send you a pdf copy.

[Will10MNT]

This one? Its the only one I've found, it doesn't go too much into detail about rescuffing the plates, just disassembly, if im not wrong. Understanding the thing is taking me a couple reads though, so I probably missed it.

[Will10MNT]

Update, im figured which surfaces are responsible for foward friction, definitely smoothed out a bit. Just wondering what to use to clean and scuff them now before rebuilding.

[Compass790]

Sorry never heard of scuffing a clutch.
Did you check the minimum thickness? I think but didnt check its the same as a YSM12 so std is 6mm & min is 4.5.
I sell aftermarket parts for those engines & no-one has asked for a clutch plate IIRC so must be uncommon for them to fail.
Make sure its adjusted properly when you re-install.

Did the gearbox get water in inside? looks rusty.
If you find out about cleaning or scuffing from somewhere else please post details as I'm curious about that.



If its reversible ( I cant remember) you could flip it over. Of course you would lose reverse if nothing else changes but that may be better than no fwd to you.


Can post a YSM12 manual which is more detailed & largely the same if you PM me.
Good luck

[Will10MNT]

https://www.cruisersforum.com/forums/f54/de-glazing-km2a-clutch-cones-95325.html
This is the post I was going off of for 'deglazing' possibly with the grinding paste. Ill have to measure my plates to check the width of them right now, thank you for that information. Im not sure about water, the gasket that went around the housing was falling apart as I opened it so maybe there? Not sure about replacing that gasket yet either, my local yanmar parts dealer isn't open until the 4th. The previous owner said he put lucas oil stabilizer in the gearbox, so im not sure if thats what caused the problem here.

[Compass790]

Originally Posted by Will10MNT

https://www.cruisersforum.com/forums/f54/de-glazing-km2a-clutch-cones-95325.html
This is the post I was going off of for 'deglazing' possibly with the grinding paste. Ill have to measure my plates to check the width of them right now, thank you for that information. Im not sure about water, the gasket that went around the housing was falling apart as I opened it so maybe there? Not sure about replacing that gasket yet either, my local yanmar parts dealer isn't open until the 4th. The previous owner said he put lucas oil stabilizer in the gearbox, so im not sure if thats what caused the problem here.

Thanks for posting link.
You may find more info about clutch deglazing on youtube.
If I was you I'd replace the crankshaft oil seal if it hasnt been done before whilst you have the gearbox off. You should be able to get an oil seal from any bearing supply place if you dont destroy the numbers on the old one.
You can use a product like Loctite 518 flange sealant or silicone instead of Yanmars over-priced gaskets. When using silicone I like to put a thin even layer on one face & let it go off overnight before bolting up. Thats how our gearbox is sealed. Use threadlocker ( loctite 242 or similar) on every bolt too as you will know they vibrate a lot.

I dont know what Lucas oil stabilizer is but if it has teflon or something like that in it that is a risky thing to do in a wet clutch gearbox.
I'd be giving the gearbox a good cleaning & refill with straight sae30 CD. We actually use 20w-50CF in our YSM8 gearbox with no problems if you cant find straight 30.

[Will10MNT]

Thank you very much for the information, ill keep this updated as I work on it again tomorrow. I'll have to get the things for the seal and bolts, and I guess just some brakelean for the clutch itself to start with.

[Compass790]

Yea Brakekleen probly a good start after a measure,
4.5mm is 0.1772 in BTW if u have imperial calipers or mike.

[Wotname]

Originally Posted by Will10MNT

https://www.cruisersforum.com/forums/f54/de-glazing-km2a-clutch-cones-95325.html
This is the post I was going off of for 'deglazing' possibly with the grinding paste. Ill have to measure my plates to check the width of them right now, thank you for that information. Im not sure about water, the gasket that went around the housing was falling apart as I opened it so maybe there? Not sure about replacing that gasket yet either, my local yanmar parts dealer isn't open until the 4th. The previous owner said he put lucas oil stabilizer in the gearbox, so im not sure if thats what caused the problem here.

Hmm... I not sure you are doing the right thing here. The 'deglazing' of a cone clutch when it is slipping is a very different thing to a slipping of a friction plate clutch (ie YSE clutch).

The cone clutch is two metal cones that are forced together by the engine torque to ensure the transfer of power.

The YSE is a traditional plate covered by the friction material. When the material gets too thin, it slips.

Maybe yours has become glazed and is slipping and maybe it is possible to remove the glazing but go carefully. If it gets too thin, it won't work.

If it is too thin and if you can't a source a new or useable second hand one, you have to replace the friction material or build up the metal plate it engages with. Both are significant undertakings.

[Compass790]

Originally Posted by Wotname

Hmm... I not sure you are doing the right thing here. The 'deglazing' of a cone clutch when it is slipping is a very different thing to a slipping of a friction plate clutch (ie YSE clutch).

The cone clutch is two metal cones that are forced together by the engine torque to ensure the transfer of power.

The YSE is a traditional plate covered by the friction material. When the material gets too thin, it slips.

Maybe yours has become glazed and is slipping and maybe it is possible to remove the glazing but go carefully. If it gets too thin, it won't work.

If it is too thin and if you can't a source a new or useable second hand one, you have to replace the friction material or build up the metal plate it engages with. Both are significant undertakings.

Glad you chimed in cobber, didnt realize his cone clutch thread was talking about metal cones.
Had a cone clutch on a previous boats gearbox that was similar friction material to the YSE 12 so just assumed ( never assume) it was the same.
I emailed him the YSM manual to give him more detail.
Worse comes to the worst he can get his friction plate relined, well at least he can here, dunno about where he lives.
Couldnt find a thickness spec in YSE manual, just a wear spec, max 2mm.
Can you find a thickness spec for YSE?
Its past beer o'clock here so manual searching performance plummeting.

[Wotname]

Originally Posted by Compass790

Glad you chimed in cobber, didnt realize his cone clutch thread was talking about metal cones.
Had a cone clutch on a previous boats gearbox that was similar friction material to the YSE 12 so just assumed ( never assume) it was the same.
I emailed him the YSM manual to give him more detail.
Worse comes to the worst he can get his friction plate relined, well at least he can here, dunno about where he lives.
Couldnt find a thickness spec in YSE manual, just a wear spec, max 2mm.
Can you find a thickness spec for YSE?
Its past beer o'clock here so manual searching performance plummeting.

Opps - I'm guilty of assuming also. The cone clutches I have messed with were metal (some sort of brass/bronze) so I ASSUMED the 2GM20 cone clutch was the same - maybe it isn't!

Nevertheless, I don't think one can just rough up a clutch plate once the material is too thin.

[Wotname]

Originally Posted by Compass790

................
Couldnt find a thickness spec in YSE manual, just a wear spec, max 2mm.
Can you find a thickness spec for YSE?
Its past beer o'clock here so manual searching performance plummeting.

Can't find a YSE clutch spec, only one for the YSM which is nominal 6mm and a wear limit of 4.5mm

[Compass790]

Originally Posted by Wotname

Can't find a YSE clutch spec, only one for the YSM which is nominal 6mm and a wear limit of 4.5mm

Ok thanks cobber, we tried to help him as far as possible to this point anyway.
He said in PM that no mechanic wants to help him. Can see why as old engine could have multiple problems & owner gets taken aback when repairs can cost more than the boat.

Awaiting next post frm OP....

[Wotname]

@Will10MNT, measure the thickness of both clutch plates (forward and reverse), it may give you some idea of the wear (or lack of) in the fwd plate.