Damper plate?

[Hayden Watson]

My boat is making a new sound at low idle when in gear and I am wondering if it might be from the damper plate. It goes away when the rpm's are above about 1400. How do you test to see if the damper plate needs to be replaced.
I also noticed today that if I have the transmission in forward, I does not rotate in one direction but rotates very easily in the other. Is that normal or a sign of future problems? I get no slipping when motoring in forward or reverse as far as I can tell.

 

[kloudie1]

It is normal for the output shaft to rotate one way and not the other. The clutch is energized by the engine torque so these typical gearboxes don't lock up like a car gearbox. It will lock/slip in opposite directions in fwd vs rev. Damper plate rattles loudly at lower rpm but hard to diagnose and differentiate from motor mounts and or shaft hitting stern tube at low rpm.

 

[jssailem]

Ah the mystery of the damper plate.

Here is an image of my old plate. The springs were loose. There was rattling. The transmission functioned smoothly once above 1100 rpm.

Having limited history my assumption was the transmission had not been serviced for more than12 years, maybe longer.

I see on my new one, installed when the transmission was rebuilt, that the springs are tight in their slots. The old ones were loose. Fingers crossed the rattling will be gone.

I read the following excerpt of shared knowledge about the Damper Plate.


THEY DON’T LAST FOREVER!
Because of their location between the engine and transmission, it is impractical to inspect drive damper plates. Inspecting them requires nearly as much time and effort as replacing them. It is sometimes possible to visually check them with a borescope or through vent holes in the bell housing; however, this cursory view may not reveal their entire condition. The normal service life of a drive damper plate is 2,500 to 3,500 hours. Usually the shock absorbing connection between the two plates is the point of failure.

WHAT HAPPENS WHEN THEY FAIL?
At best, when a drive damper plate fails, it effectively acts as if the transmission is in neutral; with no forward or reverse capability. At worst, broken metal pieces of the plate scrape, score, and damage other bell housing or drive train parts. No matter what, you won’t be going anywhere with that engine and transmission.

 

[Hayden Watson]

It is normal for the output shaft to rotate one way and not the other. The clutch is energized by the engine torque so these typical gearboxes don't lock up like a car gearbox. It will lock/slip in opposite directions in fwd vs rev. Damper plate rattles loudly at lower rpm but hard to diagnose and differentiate from motor mounts and or shaft hitting stern tube at low rpm.

That was what I thought about the lock vs slip. The motor mounts are new as of a couple of years ago and the alignment was checked last year.

 

[Hayden Watson]

Ah the mystery of the damper plate....
The normal service life of a drive damper plate is 2,500 to 3,500 hours.
...

If memory serves (which becomes more doubtful each year) I have about 2,400 hours on the old girl so should start planning on a replacement. It looks like they run about $700 unless someone knows of a lower cost source.

 

[jssailem]

unless someone knows of a lower cost source.

Would be pleased to check, but will need parts detail. ie. engine serial # Transmission#

 

[Hayden Watson]

Would be pleased to check, but will need parts detail. ie. engine serial # Transmission#

The Engine is a Universal M-25XP and the Transmission is Hurth HBW50 both were manufactured in 1987. This is the damper that CD sells for it.

 

[Waybad]

I put in a R&D from PYI they have three styles available they use a solid polyurethane center. It helps take up the hydraulic force effect of the diesel when the cylinders fire, also saving on the gears in the transmission from rattling from the shock wave. From what I read. Does seem a little quieter but not much drowns out the the diesel knock. Do not have long term use on it yet? the cost at the time was about $280.00. I am sure they have gone up.

 

[MikeHoncho]

My experience with damper plates/disc plates in autos is the cheap ones were plastic and the quality ones where springs. I’m not saying this is the case but I’d confirm and not go cheap as it’s a pain to change out normally due to access.

 

[Ward H]

@Hayden Watson Here's the link to the Catalina30 association forum where I posted my problems with finding a new damper plate.
damper plate.

 

[dlochner]

Try Fred Warner. They have good service and support.

Search – Fredwarner Marine & Outdoors

www.fredwarner.net

 

[sesmith]

I also went with an R&D damper plate from PYI on our Catalina 350 (ZF-15ma transmission and Westerbeke 35b motor). Catalina used the R&D damper plate stock on many of these boats and there were issues with low speed rattle after time. The "fix" other than a new one was a new one with more flex in it (high deflection). It's been good for 3 seasons now and about 600 hrs on it.

 

[Hayden Watson]

Well would you look at that! I was looking in my engine owner's manual for the proper idle speed and came across this.

FYI, the idle should be 1,000 - 1,200 rpm. I am definitely lower than that. I will take my digital optical tack out tomorrow and get the true reading and might as well calibrate the tack on the panel while I am at it.

The idle revs have seemed low ever since I changed the motor mounts.

 

[MikeHoncho]

The manual says 1000-1200rpm for idle?

 

[jssailem]

manual says 1000-1200rpm for idle

Seems a bit high to be shifting gears.

 

[Hayden Watson]

The manual says 1000-1200rpm for idle?

I cannot find the manual for the M-25XP but here is the one for M25XPB.

Earlier I had found one that also included the M25XP that was the same except that the max rpm's was listed as 3,200-rpm for the XP.
This table shows that 3-cylinder engines have 1000-1200 and the 4-cylinder have 800-1000.