VP sx-m cone clutch repair question/crazy idea

Frank.O

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Oct 30, 2016
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16
I know this is going to sound crazy but I still have to ask because there are number of very knowledgeable people on this forum who work on this drives
I'm getting closer to needing clutch repair. Right now slips over at 32mph
my question is what is the difference between forward and reverse gear/cup. Looking at some pics they look the same and so does the top and the bottom of the cone
if they are the same but only require different shimming why couldn't tthey be flipped including cone.
In my case the amount of pull it has in forward is not sufficient but would suffice for reverse and because neither cup nor cone on reverse would have much wear since amount of time in spend in reverse is negligible it would be in near new condition.
I hope my clutch gets me through the summer and than would do repairs either cheap or expensive way over winter.
Being machinist once it take the drive apart I will be able to measure everything and will know for sure if flipping everything is possible
 

muc

"Retired" Association of Marine Technicians...
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Why bother with all that work?
Get a left hand prop and move the shift cable to the other side.
 

Frank.O

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I thought about it but because prop shaft gears are spiral bevel with drive gear being left hand and driven right hand when prop is turning right (standard direction) gears are pushed away from each other and prop shaft bearing takes thrust load and that is corect way to run this gear set. Running them in reverse (left hand application) gears would be pulled towards each other.
As per Volvo manual left hand rotation should be ONLY used on port side in twin engine application.

​​Back to the original question would flipping gear/cups and clutch cone work. Are the gears the same? I know it would be fair bit of work but inquiring mind needs to know
I appreciate your input Muc
 

muc

"Retired" Association of Marine Technicians...
Joined
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Almost 1/2 of the SX-M drives I worked on had a LH prop on them (I mostly worked on twin engine boats) and they are exactly the same as the drives that have a RH prop on them. When Volvo sells the drive new, they don’t know (or care) what direction it will be run. When I rebuild them I do change the shimming slightly if it’s going to be used with a LH prop, but very slightly. You’re confused about the prop shaft bearing, it gets it’s load from the prop — not the gears. It’s the pinion gear that you need to worry about, but the lower drive shaft has opposed tapered bearing the hold the pinion gear in place. I don’t see any difference in the wear between a LH or RH Volvo drive. It’s the Alpha LH drives that wear out much faster.

But it back to your original question. The clutch shouldn’t be flipped—- it’s marked “this side up” I agree it looks the same, but I’ve never installed one upside down, so don’t know what would happen. When I order a new set of gears there’s no top or bottom gear, So they are exactly the same. But once they have been run awhile the gear teeth will develop a drive and coast wear pattern on them. When we rebuild these drives, we mark the gears so they get reinstalled back in the same place for this reason. Could you swap them? Maybe, I suppose it would depend on how much wear there is. I’ve never done it wrong so I don’t know. But you would have to replace the 4 bearings because they have spent their life spinning one direction.

For less work and money, you could just buy a new clutch and lap the cups.
Or try a LH prop and see if it messes up how the boat rides —— it might, depends on the hull.

Are you using Volvo gear lube? That’s the number one reason for cone clutch slipping——- wrong lube!
 

Frank.O

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Many very good points Muc. Will go with cone replacement and deglazing the cup. If I have time I will measure everything for future reference. One thing I am puzzled about is why use the old cone to lap the clutch cup. Wouldn't lapping with a new cone make better sense because I would also be matting a new cone to the old cup while deglazing the cup. I will have to figure out if the clutch shoe needs updating. I will report back with my findings
I rulled out left hand prop since my boat already has slight list to start board. Introducing more lift to port side would be bad thing for higher speeds
 

muc

"Retired" Association of Marine Technicians...
Joined
Jul 7, 2004
Messages
2,244
The new cone has a coating on it. Very important to keep it intact.
The coating on your old clutch is gone now. You need a new one.

Many years ago. When we would order lube from Volvo. It would come in Mobil One 5 gallon pail with a Volvo sticker on it. But it seems something must have changed. Now I highly recommend Volvo lube ONLY in these drives.
 
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