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Old 27-09-2019, 19:24   #16
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Re: Removing coupling nut on 72 series borg warner or velvet drive

From new they have that bulge. Yeah , the seal is the very last thing to do after the tedious filing grinding bit. How's the bearing? Look closely at the cone between the rollers, it, rather than the cup is often where the wear is.
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Old 27-09-2019, 20:26   #17
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Re: Removing coupling nut on 72 series borg warner or velvet drive

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Originally Posted by phorvati View Post
So it's exactly what you said. Nut was loose. Bearing is in great shape. But torquing the nut to 200ft-lbs made rolling torque around 120 in-lbs. Way more than 30 in-lbs. 120 in-lbs is more a breaking torque. It took that much to get tranny rotating .I imagine that rotating torque is a lot less. Hard to measure, I would need a strain gauge or something and a lot more room. So better question is what do they call rolling torque?


The rolling torque is the amount that it takes to keep the coupling turning after the initial breakaway. It's the resistance of the gears and the minute amount of preload (or no preload at all). Borg warner give us these figures mainly to avoid loading up the bearings. The perfect situation is zero endfloat at 200ftlbs on the nut but as you know , that can be a false situation so they give us a rolling torque to ensure that we don't screw it up. Basically the same torque that exists with the nut just finger tight( if that were possible with a nylon nut )
After you get this back together it would be wise to check the engine alignment to exclude that as a reason for the coupling being a bit loose on the gearbox.
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Old 28-09-2019, 11:52   #18
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Re: Removing coupling nut on 72 series borg warner or velvet drive

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Originally Posted by skipperpete View Post
The rolling torque is the amount that it takes to keep the coupling turning after the initial breakaway. It's the resistance of the gears and the minute amount of preload (or no preload at all). Borg warner give us these figures mainly to avoid loading up the bearings. The perfect situation is zero endfloat at 200ftlbs on the nut but as you know , that can be a false situation so they give us a rolling torque to ensure that we don't screw it up. Basically the same torque that exists with the nut just finger tight( if that were possible with a nylon nut )
After you get this back together it would be wise to check the engine alignment to exclude that as a reason for the coupling being a bit loose on the gearbox.
Thanks. As I took everything apart again few things I learned. Previous owner mentioned something about getting towed in by the coast Guard and having work done in Beaufort NC on tranny and stern tube. Well now that I torked the nut to 200 I am realizing that original nut was never crushed. I.e. now the washer is off an thread seal is cracked where initially it wasnt. That might have something to do with it being loose, almost just hand tight. And my collapsible washer is in pic below.
So I'm just going to get few spacers sent overnight for Tuesday and put this back together. With few extentions I was able to get the wrench outside of the boatClick image for larger version

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Old 02-10-2019, 05:27   #19
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Re: Removing coupling nut on 72 series borg warner or velvet drive

Got 2 new spacers yesterday, The longest available and one that's in the high mid range. Tried the longest and didn't like how much end play there was after I torqued it. So I used the smaller of the two I bought. That felt like there was barely noticeable end float after I torqued it. Then I installed the seal and put rtv in the cavity and did the final install. Once rtv dries I'll run it before launch. But this feels like leak should be gone. Also took the time to disconnect aft isolation mounts and shift the engine to port about 3/16". That made coupling flanges line up better. It seems it was a left right alignment issue. Up/down looked good.
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Old 02-10-2019, 16:20   #20
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Re: Removing coupling nut on 72 series borg warner or velvet drive

Thanks for the update and congratulations on getting the job done.
There are several previous threads on the forum addressing the black art of engine alignment, it's never quite as easy as it might seem.
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Old 26-03-2020, 22:06   #21
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Re: Removing coupling nut on 72 series borg warner or velvet drive

Hello all, new here so hope this is going in the right spot.
I have a 1987 Carver Aft Cabin with original twin I/B Merc 340hp, mated to velvet drive 10-18-010 with 2.57 reduction gears on the tail end.

My question is regarding the reduction gear output seal. Built the metal bar and broke the nut loose, however mine has a castle style nut on it instead of the nylock. Does this nut still have to be replaced?

200ft lbs is the correct torque for this nut?
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Old 27-03-2020, 05:27   #22
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Re: Removing coupling nut on 72 series borg warner or velvet drive

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Originally Posted by Stormwind83 View Post
Hello all, new here so hope this is going in the right spot.

I have a 1987 Carver Aft Cabin with original twin I/B Merc 340hp, mated to velvet drive 10-18-010 with 2.57 reduction gears on the tail end.



My question is regarding the reduction gear output seal. Built the metal bar and broke the nut loose, however mine has a castle style nut on it instead of the nylock. Does this nut still have to be replaced?



200ft lbs is the correct torque for this nut?


Hi Stormwind83
If there is no locking method built into the flange nut ......... no deformation on the outer edge, no fine slice to make the nut bind then you can use the nut again.
Iíve never seen a castle style nut on a Borg Warner velvet drive, usually theyíre just the regular nyloc type. 200ftlbs sounds pretty good for the torque but if you havenít got a tension wrench you can pull 100lbs on a 2í long socket bar and youíll be pretty close.
Cheers, Pete.
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Old 27-03-2020, 05:48   #23
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Re: Removing coupling nut on 72 series borg warner or velvet drive

BW built Velvet Drive transmissions with 2 different sized output shafts using 2 different sized nuts depending on model or age, I donít remember
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Old 27-03-2020, 05:57   #24
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Re: Removing coupling nut on 72 series borg warner or velvet drive

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If itís leaking it will probably be hand tight. I use a block of wood braced against one of the bolts and the hull to loosen the nuts. After you pull the coupling and clean it and the splines, replace the coupling and fill the cavity with RTV sealant and put on a NEW nut. It will push the RTV into the splines and seal it. Torque to 200 ft/lbs the best you can. The nut is a one time use.
Yah , something like that , somethings a length of steel , With holds and bolted on to the flange works better at stopping rotation
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Old 27-03-2020, 06:22   #25
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Re: Removing coupling nut on 72 series borg warner or velvet drive

Yes, drilled a piece of flat iron to hold the flange and I was able to get the nut to 200 ft lbs. with a 1/2" torque wrench along with the Rtv on the spines!
Thanks!

The input shaft seal on the front of the tranny looks like an easy pop out and replace. Is there anything else to know about that one?
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Old 27-03-2020, 06:26   #26
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Re: Removing coupling nut on 72 series borg warner or velvet drive

I’ve even used a D shackle thru the flange and a steel pipe

Many ways

Normally the problem is working space

Some installations are very difficult
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