Damper plate failures HELP111

[AVATRICE]

Hello,
My name is Captain Sharon. I am owner/operator of a live-aboardsailing school for women in Maine. This is my 21st year in business.
I sail a 44' Pearson Countess ketch. 1966
In 2004, we re-powered with a 6 cyl 120 HP Westerbeke with a Borg Warner Velvet Drive transmission.
The new installation was a bit rocky with a pretty significant vibration issue which was eventually resolved.
The 1st transmission failure was at 400 hours in front of the customs dock in Bermuda. Another failure occurred in the Bahamas in 2010. We were fortunate to discover Stela Maris Marina on Long Island.
Since that time, we have had 4 damper plate failures and either a transmission rebuild or replacement . We currently have 4000 hours on the engine.
I have asked our mechanics/installers, Westerbeke tech support, sales people and managers, what can possibly be the problem. I have received many responses, but no answers .
The most memorable response was from the Manager of Hansen Marine in Marblehead, where we purchased the engine. "Well, Sharon, maybe you just need to consider a replacement of the damper plate as part of your annual maintenance."
You can imagine my reaction to this flip response.
Thousands of $$$$ later, I am reaching out to find out if anyone has had or know of a similar issue.

[transmitterdan]

Dear Sharon,

Welcome to CF. There are a lot of knowledgeable engine/transmission people here.

I have a few questions for you:

1) Under what conditions does the plate fail?

2) Exactly how does the plate fail? Does it fly apart into pieces? Or does it just start rattling a lot?

3) It seems like an overly large engine for a 44' mono. What was the size of the previous engine?

4) What is the HP rating of the transmission? Or what is the exact model # of the transmission?

[boatpoker]

Sharon : try a damper plate with polyuretnane disc instead of springs, quiter, smoother and much more long lasting ..... one of my wiser aquisitions

[leftbrainstuff]

Misaligned trans to engine and an unusually high shift duty cycle would be my starting topics based on you having recurring issues.

The velvet drives do have that characteristic rattle when the springs lose tension.

The velvet drives have a very short life in reverse. They are designed for sustained use in forward but not reverse.

You arent running a left hand trans in a right hand drive application are you? They build handed trans for dual prop powerboat applications.



Sent from my SM-N900T using Cruisers Sailing Forum mobile app

[captain mitch]

WOW, damper plates just do not fail that often, usually its rusty springs that just fall apart. That being said --
Velvet drive transmissions have a pretty high tolerance for shifting at higher torque, (we had them in all our ski boats which saw severe shift duty and seldom killed a clutch pack).
I would have to look at doing a dial run-out on the crank at the mounting flange, and the flywheel- rare, but the flange may be running out causing the plate to fail early --OR perhaps the rather typical velvet drive rattle at low idle speeds may be being "sold" to you as plate failure.
That does not explain the trans failures though, unless the failure there is in the input shaft seal/bearing area -- that would tie back to the run-out of the crank and flywheel.

[reed1v]

Would also check your prop size. We switched to maxi props in all our boats and that solved a lot of issues. A previous post mentioned alignments. Would also suggest shaft be checked for trueness. Long shafts can bend over time. Finally, check the rpms you are using when shifting into gear. With that giant engine, anything above 300 rpm may put too much stress on the plates.

As a point of comparison, our old perkins ran 30,000 hours without a problem with the transmission, engine, nor shaft bearings. That is a bit under 20 years worth of use.

[Xthewater]

Damper plate comes into play when shifting to reverse to reduce the shock. If done at high rpm's repeatedly it won't last long. I am also curious as to the source of original vibration and what was done to resolve it? Vibration can transmit into the damper through the transmission increasing wear also not good for the transmission btw.

[coastalexplorer]

Maybe a bit off topic....But..does anyone in the Pacific Northwest have a scrapped Volvo Penta MS2B transmission. or alternatively any MS2B-A, MS2B-L, and MS2B-R that they are prepared to either lend. donate, or sell cheap for the purpose of some reverse engineering investigation into a solution for failed splines and damper plates. Pls private message me.

[DSW]

It could be a torsional vibration issue from the engine which is destroying the damper plate and damaging the gearbox, the engine manufacturers should be able to carry out torsional vibration calculations for the whole drive train to rule this out or advise necessary damper/coupling changes. You also say that "The new installation was a bit rocky with a pretty significant vibration issue which was eventually resolved" what was the issue and how was it resolved.

[DSW]

Hello Sharon, further to my previous post is it the Westerbeke 120-N6 engine, if so I note from their website that it was specified with a Hurth ZF45A Transmission not the Borg Warner velvet drive. This again raises the question of engine gearbox compatibility, who checked this, who matched the gearbox and drive coupling/damper plate to the engine?

[HappyMdRSailor]

Hi Sharon,

Lot of good info here thus far... As above...

Tranny model no?...
What was the vibration and what was the resolution?
Crank runout check...