Damper plate replacement how-to

A couple recent threads on bluewater and such have me thinking about preventative maintenance on my damper plate of my old Borg Warner velvet drive coupled to my Perkins 4.236. Not something I've ever done. Parts are cheap enough so I thought I'd bring a damper plate with me when I return to Weebles in late October.

Any good videos of how-to videos y'all can recommend on replacing the damper plate, preferably on a Perkins 6.356/4.236 natural? Any other parts I should bring with me whilst doing this? Looks pretty straightforward but I'm not the best wrench going so some mentoring would be helpful.

Thanks in advance

Peter

When I did my Lehmans damper plates it was very easy except for a couple of stuck bolts. However I had pulled the engine and transmissions up out of the engine room. So it was simple to slide the transmission back enough to get to the damper plate. If the engine was still installed it would have been much more difficult since I wouldn’t have had enough room to slide the transmission back. The shaft wouldn’t have slid back far enough without pulling the props. It depends on how much room you have behind the transmission. Other than that it just took standard tools and about half an hour.

When I did the 120's in the water I just slid the shaft back after unbolting and marking. Unbolting peripherals and the trans should be obvious. None of my bolts were seized so all went smoothly.
It is getting the trans out of the way to unbolt/bolt the damper was the biggest issue. Room to work.
In my case I wrapped two lines around under trans and myself plus another on each end manhandled away.
My engine had rear mounts, if you do not then block it first.
Assembly is bolt it together. The shaft alignment is where more attention is needed.
No I did not make a you tube video.

Assuming that your engine mounts are not on the transmission you can get the same thread size bolts but much longer and put 2 in the top of the transmission and you can slide the transmission back on the bolts using the bolts to hold the weight of the transmission while you are wrenching on the damper plate.

I had to change one of mine last month because it broke. No warning, just suddenly no thrust from that engine. Fortunately it's twins so I limped in on the other engine. So yes, they can fail without warning so some preventive maintenance is advisable. I changed it in the water and the biggest problem was I couldn't slide the shaft back far enough to get the Velvet Drive off the mounting studs. I had to jack the Perkins 6.354 up high enough to clear the coupler flanges, it weighs about a ton. I used a small floor jack with plywood under it. Scary, but it worked. If doing it out of the water you could pull the prop off and get all the clearance you need. The aft engine mounts are on the trans so I had to block the engine up with wood blocks and plywood. Once the trans is off just pull the bell housing or bell housing cover off and there's the damper plate. Mine were the 8" type with 9 little Allen head screws holding them on, I had to drill 2 of them out. The flywheel was also drilled and tapped for an 11" plate so I bought one of those from fredwarner.net, $147.00. Transatlantic Diesels quoted $280.00 for the same plate.
I'm guessing the other plate is nearly as bad, I'll change it out after haul out this fall so I can pull the prop to get more clearance sliding the shaft back. I'll still have to jack the engine to get the mounts off, but only about a 1/4 inch.

I've never had to do a damper plate, but one thing to watch with the Velvet Drives is the reduction units. Both of mine have had the same issue over time. One gave some noises as a warning (but quit before the cause was found, before I had the boat so I didn't witness this one). The other one didn't make a sound. Was perfectly fine until it wasn't. Cruising on plane it felt and sounded like the port trans just slipped into neutral. I was in the galley when it happened and it didn't make any noise on failure.

The failure in both cases was the stationary plate that keeps the outer shell of the planetary reduction gear from rotating. Not sure what the starboard one looked like, but when the port failed, it sheared all of the teeth right off the stationary plate. No collateral damage, just slid the shaft back, pulled the reduction housing. Overnighted a new stationary plate and reduction housing gasket, cleaned the junk out of the trans, and reassembled. It's been fine for ~450 hours since then.

I'm not sure what caused the failures in my case, as I haven't heard many other mentions of it happening. Not sure if it's related to how much power is going through the trans (340hp through a velvet drive 72C in my case) or if it's more related to the shock loads when shifting or something like that.

Weebles is out of the water so that might help, but I'm not keen to drop the rudder as there is a shoe beneath the rudder and - the Wagner T-Ram steering is a bit trickier than a standard hydraulic cylinder. I also have to replace the Tides dripless seal (I have a spare on the shaft).

I am not sure if I have a 71C or a 72C transmission. I have someone going to the boat this week to see if they can snap a picture of the build plate. Conceptually I understand the process but it's been 30-years since I've pulled a transmission on anything (I used to ride a R75/5 BMW motorcycle that developed a rear main seal ona long trip - I'd find a shade tree and pull the tranny every 700 miles or so to clean-out oil to avoid saturating dry clutch plates, similar to automotive).

I'll see if I can find an exploded parts diagram somewhere. Sounds like some Hex-head sockets for a 3/8" socker drive might be in order. Any idea on size?

Thanks guys - very encouraging (except for jgwinks comment about drilling out two bolts).

Peter

71C vs 72C matters for the main body of the trans, but as far as I know the reduction units are identical between the 2 models. 71C vs 72C differences are related to power handling, and the 72C main body has a 1.1:1 reduction in reverse on top of whatever the reduction unit provides, the 71C does not (forward and reverse ratios are the same).

8/18/24 Gentlemen, Just seeing this thread.
Opinions sought.
I opened the hatch to check the engine room while cruising at 8 mph and found about 1-2 cups of oil in the drip pan. IR thermometer showed 325 degrees F. Slowed to idle, kept in gear , added back about two cups Rotella 30 wt. In about 30 minutes the temp was at 260 F. Shut that side down. Got in on other engine. BW 10-14-000-003 velvet drive, a 71 c, I believe. I figure it’s cooked and am about to have removed for me to deliver to Chris Jones in Summerville SC for rebuild.
Any comments? Suggestions?

mvweebles said:

Weebles is out of the water so that might help, but I'm not keen to drop the rudder as there is a shoe beneath the rudder and - the Wagner T-Ram steering is a bit trickier than a standard hydraulic cylinder. I also have to replace the Tides dripless seal (I have a spare on the shaft).

I am not sure if I have a 71C or a 72C transmission. I have someone going to the boat this week to see if they can snap a picture of the build plate. Conceptually I understand the process but it's been 30-years since I've pulled a transmission on anything (I used to ride a R75/5 BMW motorcycle that developed a rear main seal ona long trip - I'd find a shade tree and pull the tranny every 700 miles or so to clean-out oil to avoid saturating dry clutch plates, similar to automotive).

I'll see if I can find an exploded parts diagram somewhere. Sounds like some Hex-head sockets for a 3/8" socker drive might be in order. Any idea on size?

Thanks guys - very encouraging (except for jgwinks comment about drilling out two bolts).

Peter

Click to expand...

A yard tech pulled mine out so I don't know the exact size but they looked like 1/4", maybe #10. He actually used a star drive socket and drove it in with a hammer. Likely a metric size to allow that. This was an 8" plate with 9 bolts. I replaced it with an 11" plate with 6 3/8" grade 8 hex head bolts. Yours could be either, the hex heads would be a lot easier to remove. I hate Allen heads. When I do the other one I'll get another 11" and just grind off any of the Allens that fight me. I won't need them.

I should have stated that the oil in the drip pan was from the transmission

Billywilly said:

8/18/24 Gentlemen, Just seeing this thread.
Opinions sought.
I opened the hatch to check the engine room while cruising at 8 mph and found about 1-2 cups of oil in the drip pan. IR thermometer showed 325 degrees F. Slowed to idle, kept in gear , added back about two cups Rotella 30 wt. In about 30 minutes the temp was at 260 F. Shut that side down. Got in on other engine. BW 10-14-000-003 velvet drive, a 71 c, I believe. I figure it’s cooked and am about to have removed for me to deliver to Chris Jones in Summerville SC for rebuild.
Any comments? Suggestions?

Click to expand...

If it got hot likely the clutch plates were slipping. I don't know of anything else that would do that. It should be repairable. What's the max RPM of your engines? The Velvet Drive manual says to use ATF but straight 30 weight is allowable if the max RPM is below 3000. Mine redline at 2750, they had what looked like 30wgt when I bought it so that's what I've been using. Don't know if that could cause overheating. I cruise at 1800-2000. My gears run just warm to the touch, about 90-100F or so.

Billywilly said:

8/18/24 Gentlemen, Just seeing this thread.
Opinions sought.
I opened the hatch to check the engine room while cruising at 8 mph and found about 1-2 cups of oil in the drip pan. IR thermometer showed 325 degrees F. Slowed to idle, kept in gear , added back about two cups Rotella 30 wt. In about 30 minutes the temp was at 260 F. Shut that side down. Got in on other engine. BW 10-14-000-003 velvet drive, a 71 c, I believe. I figure it’s cooked and am about to have removed for me to deliver to Chris Jones in Summerville SC for rebuild.
Any comments? Suggestions?

Click to expand...

A 10-14 is a CR2, the front end of which shares some commonality with a 71, but is otherwise different. They’re good transmissions but haven’t been made in a long time so parts are rather scarce. That said, the folks who really know how to fix them seem to be able to get parts. If you had it up to 325 degrees then there definitely would be internal damage, probably clutches but will need to be thoroughly checked.

Ken

Thank you very much for your responses. Hopefully pulled this week. Rebuilder, Chris Jones, says a month to process the rebuild.
I failed to say I’ve still got forward and reverse gear. Used it only to dock twice in leaving for, and arriving at the boatyard.
Thanks again
Bill

Forgot. WOT is about 2600. 185 hp Perkins T6.3544M. Cruise 1050-1300.