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[Colonel Butler]

It is the end of the boating season here in Niagara so after haul out last week, I decided to remove the transmission and investigate the condition of the damper plate. I'm assuming it is the original, a R&D 22B4. Seems to be in perfect condition. Splines on both the damper and transmission show no excessive wear. Very little backlash in the gearbox. After looking at this forum, the C350 and the C36 forum, I get the sense that a change in damper flexibility may eliminate or reduce the rattling noise which is a product of a lightweight flywheel on this engine combined with low RPM.

PYI (the North American agent for R&D) sell more flexible dampers. The original 22B4 has a deflection of 3 degrees. They sell a high deflection model 22AM4 that has 30 degrees deflection. I would like to hear from other owners that have tried to get rid of the low speed rattle by changing the damper and what type of damper has worked or not worked. I am also considering installing the R&D flex coupling insert.

I won't be reassembling until the spring so I have lots of time to research and make my decision.

Thank you

[Stu Jackson]

Nice report, thanks.

IIRC, the C36 skippers seemed to have more transmission and damper plate issues than "we" C34-ers ever have reported.

I'll go poke around the C36 Forum.  You could, too.

Also superb of you to post about something BEFORE you did and wondered...doh!

Thanks again for bringing up this issue.  I still have no idea why the C36 folks had to suffer:  same engines, essentially same boat.  But they have recorded and shared their experiences.

Now we just gotta find it. 

[Jim Hardesty]

Colonel,
A suggestion.  To your signature add your boat details and your sailing area.  It helps getting the best answer to your questions.  Take a look at what others have done.
How low is your idle speed?  What RPM do you get the chatter?  I don't notice any chatter on Shamrock but is rough at RPMs below the recommended idle.
Jim

[Stu Jackson]

OK, here's the first one I found on the C36 site from a search on "damper plate".  Many more show up, for different engines.

https://www.catalina36.org/forum/technical-discussion/damper-plate

Now that you can get to the C36 forum so easily, please feel free to search away there.

Please also let us know if/when you find something pertinent to your question.

Good luck.

edited to include link

[Colonel Butler]

In answer to the question about what RPM I hear the rattling, it occurs when in gear between idle (900 RPM) and seems to go away at around 1100 RPM. Very annoying when low speed maneuvering. Also, just can't be that good for the gearbox. I spoke with another Catalina owner (C310) at our club who had "the noise" and his transmission failed. He had it rebuilt and installed the Sach's spring type damper plate and all is well now. His was the M25 Universal engine.

[Roc]

Not sure if the boat is new to you, but there is a normal chattering of the damper plate at idle and goes away at the RPMs you state.  What you may hearing is normal.

[Jim Hardesty]

Not sure if the boat is new to you, but there is a normal chattering of the damper plate at idle and goes away at the RPMs you state.  What you may hearing is normal.

Thanks Roc,
I've been following this discussion thinking that Shamrock may have a problem.  You put my mind at ease.  Others have described the noise as quite bad, not Shamrock, I don't believe.  Not many newer Catalinas around here to compare with.  I thought it was rough diesel idle.  Don't think it's change in over 1000 engine hours.  But my hearing has, worries me that I may miss a developing problem.
Jim

[Roc]

The chatter I hear (it is quite loud and sounds horrible, like someone flailing maracas), has been like that since the boat was new when idling in gear.  It has not changed.  It disappears at around 1000-1100 rpm.  If I'm moving at idle, I usually toggle between forward and neutral anyway.  Or if I need to keep moving at idle, I just inch up the throttle at just the point of becoming quiet.  I don't like to keep the boat in gear at idle just because I don't like the sound and I'm thinking having it chatter extensively, can't be doing any good.  But it is normal.  I understand there are newer damper plates of a different design that don't chatter, or at least much less intense, than the one's in our boats.  I'm guessing the damper plate is an old design, and newer Catalinas probably use the most current design without the chatter.  Also, if the diesel is Yanmar, or other brand than the "Universal" in ours, that trans design must be different and may not chatter.

[Jim Hardesty]

If I'm moving at idle, I usually toggle between forward and neutral anyway.  Or if I need to keep moving at idle, I just inch up the throttle at just the point of becoming quiet.  I don't like to keep the boat in gear at idle just because I don't like the sound and I'm thinking having it chatter extensively, can't be doing any good.  But it is normal.

I do the same.  Now that I've read about it will probably notice it a lot more.
Jim

[Breakin Away]

Yes, all this sounds very familiar. Now I have something to worry about. Hopefully the winter will be long  enough that I'll forget about it by next spring. 

[Geoffreykwright]

Sundowner III (Cat 34 Mk II, Hull 1494, year 2000) chatters A LOT when in idle forward...speed it up a bit and goes away.  Neutral is fine.  Not 100% sure at what RPM the chatter goes away since I think my tach is off.  She's put away for the winter now, but I plan to check the accuracy with a laser tachometer in the spring.

Does this sound like what others are describing?

[Jon W]

I may have missed this but how did you identify the noise was from the damper plate? Did you go below while in fwd with the engine covers off and engine exposed?

[Colonel Butler]

My conclusion that the chatter was induced by the damper plate was based on some research of the C36 forum and the experience of a C310 owner at our club who had similar noises on his M25 engine. He cured his low speed clatter by changing to a damper plate that had less stiffness.

To me it sounded like a the pulsations from the diesel at slow speed were not dampened sufficiently by the flywheel or the damper plate and the rattle sound was from low load backlash in the gearbox. (I'm a mechanical engineer and spent my 37 year career in power plant maintenance). I just don't think that exposing the gearbox and splines to that sort of service would be good in the long haul. I just purchased the boat with only 370 hours on the engine so would like to address it now.

The damper plate was in perfect condition. In talking to the rep at R&D, I discovered it was the stiffest version and they have two others with more flexibility. I'm going to order the most flexible version on their recommendation and install it next spring before launch. Will update the forum on the results.

[Breakin Away]

Your hypothesis sounds very plausible. Thanks for posting.

Going by memory, my motor idles at about 800 RPM and chatters when in gear. The chatter disappears at 900 or 1000 RPM, and I'll quickly put it at that speed after shifting into gear. I am tempted to readjust the idle speed to 900-1000 to work around the problem, but of course shifting at a higher speed could create other problems. If I also have a stiff damper plate, would that better facilitate shifting at the slightly higher speed without causing any damage to motor or transmission?

[Jon W]

Guess I'm lucky. I had various chatter/clatter/vibration noises at 850-1000 RPM in forward on my MK1 M25xp. It would go away then return around 1800, then quiet and smooth at 1900 RPM and above. Turned out to be the grates on the stove, companionway stairs, poorly stowed companionway drop boards, galley plywood floorboard, aft cabin and head doors. Some grate clips, felt pads, and dedicated storage for drop boards made a dramatic improvement. Still have some vibration noises. I don't think it's related to the damper plate, but will be paying more attention. Thanks for posting.