Prop Chatter advice

gpd955 · Aug 2, 2011

bobgelb@gmail.com said:
Is this the normal noise from a Catalina 310 prop at low rpm or could it be something more critical that i should be looking at.

At around 1800rpm I get a vibration that I can feel at the helm. I am assuming that, since it happens consistently at that RPM (and that with a lot of sea activity, the quality of the vibration caries), the vibration is cavitation. There has been no effect on performance or speed. It was there when I bought this boat last year and the prop was in good shape at survey and when I pulled the boat. The shaft is also straight. Had a diver check the bottom and the zinc last week and it all still looks good. The noise disappears below and above that general range. I am interested if your problem is the same as mine. I would love to get it taken care of so I don't damage the prop and so I don't have to stay above or below that RPM in order to preserve my sanity!

Don S/V ILLusion · Aug 2, 2011

Bob
If you are not confusing vibration with chatter, I'd suspect it isn't the prop at all but rather the clutch plate in the transmission. You might want to take a closer listen to the source.

Don S/V ILLusion · Aug 2, 2011

Bob
That's the sound of a clutch plate wearing which is a slow process so usually not an emergency. Usually evident at slow RPM or when changing gears when the plate isn't fully engaged. If it is the clutch plate, the fix requires removal of the tranny but if it were me, and it was a couple of years ago, I'd wait until the end of your season when you pull the boat to do it/have it done. Obviously, the first step is to confirm that is the problem and the only way to do that, short of removal, is to make sure that is the location from which the chattering is coming.

Witzend · Aug 3, 2011

Please refer to the following thread:
http://forums.catalina.sailboatowners.com/showthread.php?t=113844&highlight=damper+plate

rpwillia · Aug 3, 2011

Retrospection

Witzend said:
Please refer to the following thread:
http://forums.catalina.sailboatowners.com/showthread.php?t=113844&highlight=damper+plate

Witz, In retrospect on this, do you think the overall mis-alignment you had with your struct helped cause some of your problems with the damper and the motor mounts?

Witzend · Aug 4, 2011

No, It just wore the cutlass bearing out faster from uneven pressure. The transmission is in between the mis-aligned strut and the damper plate, isolating any lateral forces applied from the drive shaft.
The reason for the problem was 2 fold:
1) The transmission alignment pins to the bell housing were mis-aligned causing the input shaft of the transmission to be out of alignment to the engine crank shaft causing lateral forces to be applied to the damper plate. This became apparent when putting the transmission back on, it would not mate properly to the bell housing. My guess is the mounting plate for the transmission is what was incorrectly made, because I find it improbable the the bell housing casting some how was wrong.
2) The R&D damper plate used was also too stiff as rated for the M25, so while at idle speed it could not isolate the torsional vibration out of the system and once a little play got started on the spline it just tore the damper collar up.

What is surprising to me is other than the wear on the input spline (which became a non-issue because of the new mounting ring pushing the interface beyond the wear point) that there was no apparent damage to the transmission from all this.
BTW I now have ~ 200 hours on it, and still quite and smooth as butter.

rpwillia · Aug 5, 2011

Thanks

I am still monitoring mine. I may pull the transmission and check it out this winter. I did get a pretty bad rattle this year, but in diving under the boat I found the zinc was a bit loose so I tightened it up.

Tom J · Aug 6, 2011

A couple of things I've noticed on my M25-xpb. First, the engine is never very smooth around 1800 RPM. Could this be because it is a three cylinder, and harmonic vibrations are introduced? Secondly, the set screws on the prop shaft coupling flange were loose, though the safety wire kept anything bad from happening. Once I tightened up the set screws, the whole system ran much smoother.
By the way, I do get some rattling from the damper plate, but it's been that way for over a thousand hours, so at this point, it almost seems "normal".

Witzend · Aug 6, 2011

Tom J said:
By the way, I do get some rattling from the damper plate, but it's been that way for over a thousand hours, so at this point, it almost seems "normal".

Did you see the pictures of mine after only >500hrs. Seems like maybe your noise is from something other than the spline/collar play. It was a clacking noise under 1500 RPM, loudest at idle. The R&D damper in mine is a plastic ribbon, that cracked and failed.
The correct Sachs plate uses springs. The contact points from the springs against the two plates is what normally wears.

Tom J · Aug 9, 2011

Witzend said:
Did you see the pictures of mine after only >500hrs. Seems like maybe your noise is from something other than the spline/collar play. It was a clacking noise under 1500 RPM, loudest at idle. The R&D damper in mine is a plastic ribbon, that cracked and failed.
The correct Sachs plate uses springs. The contact points from the springs against the two plates is what normally wears.

Thanks for the pics. You're problem is definitely different than mine. I have found other sources of rattling noises and secured them. One was the oil drain hose, where the cap is secured in its fitting. Putting a zip-tie around the cap and fitting got rid of a lot of noise. Yesterday, I found the pins in the center of the aft engine mounts loose and rattling. Put zip-ties on them, too. All in all, my propulsion system is operating smoother and quietier than ever, so I can't complain.

Stu Jackson · Aug 15, 2011

I have what I believe is almost a unique experience. My coupling bolts ocaissionally work themselves loose, and we get a distinct vibration, a different kind of "feeling" underfoot that I can only describe as a "thrumming" over and above the "normal" sound the engine makes. When this occurs, I hop down below and usually find one screw and nut has worked itself loose, and is simply laying there waiting to be reinstalled. Since there's no room in front of the coupling to insert the bolt, I have to work in the blind to get the nut back on.

This, of course, is in addition to the normal sounds and rattles our three cylinder beasts make.

The C36 guys had a lot of trouble with the damper plates on their engines - big time. But Witz' description and pictures are best ones I've ever seen.

Witzend · Aug 16, 2011

Stu Jackson said:
I have what I believe is almost a unique experience. My coupling bolts ocaissionally work themselves loose, and we get a distinct vibration, a different kind of "feeling" underfoot that I can only describe as a "thrumming" over and above the "normal" sound the engine makes. When this occurs, I hop down below and usually find one screw and nut has worked itself loose, and is simply laying there waiting to be reinstalled. Since there's no room in front of the coupling to insert the bolt, I have to work in the blind to get the nut back on.

This, of course, is in addition to the normal sounds and rattles our three cylinder beasts make.

The C36 guys had a lot of trouble with the damper plates on their engines - big time. But Witz' description and pictures are best ones I've ever seen.

Try some Locktite on them, or use the nylon topped nuts.
BTW, thanks for the nice comment Stu! So far all is still good with a couple of hundred hours on it.

rpwillia · Oct 30, 2011

Pull the Tranny and Damper Plate today

Turned out to be a lot easier than I thought. I saw the Westerbeke rep at the Annapolis boat show and he told me I could pull the transmission off of the back and the pull the damper plate out of the opening, and he was right. Took about 1.5 hours.

I was really doubting I would get the damper plate out the opening, but as soon as I pulled the last last bolt out the plate just slid right out. I have the R&D 2284 damper plate which I am going to replace with the Sachs one. No parts or pieces in the bottom of the bell housing

, but when I shake the damper plate there is a rattle in it. Also the teeth on the damper plate are pretty worn down, but the teeth on the transmission shaft look nearly brand new

; but the overall result a lot of play between the shaft and the damper plate.
To avoid PaulJ riding me

ix:I am also posting the pictures. Needless to say, this most strongly appears to be my problem and I am pretty happy it is just a simple damper plate replacement. :dance: There is also a picture of my transmission and it is a Hurth ZF 5 H.

Witzend · Nov 2, 2011

Hey Ray, Same problem I had, only yours was not as bad.
So you did not even have to separate the bell housing? I did not think you could get it the damper out without doing that. Anyway are you going to put another R&D in, or find another plate. I could not find one that had the right torque rating that would mount up the the fly wheel. So I had to salvage the mounting plate from the R&D and mount the Sachs to it. If you end up going that route, make sure you have all the run-out out of the system, or it will just eat it up again. BTW, grease the shaft up before you put it back together.

rpwillia · Nov 5, 2011

Reply for Witz

Witzend said:
... So you did not even have to separate the bell housing? I did not think you could get it the damper out without doing that. Anyway are you going to put another R&D in, or find another plate. I could not find one that had the right torque rating that would mount up the the fly wheel. So I had to salvage the mounting plate from the R&D and mount the Sachs to it. If you end up going that route, make sure you have all the run-out out of the system, or it will just eat it up again. BTW, grease the shaft up before you put it back together.

Witz, I did not have to pull the engine; I simply disconnected the transmission from the bell housing and pulled it away. Then I was able to reach in through the back of the bell housing to unbolt and remove the damper plate. I did get a Sachs damper plate and I am going to do what you did and salvage the R&D mounting plate, and perhaps some extra spacers and longer bolts, to mount the damper plate back a little so it mates nicely on the transmission. There is a hair bit of play on the end from wear (not near like what you had) and I could probably pass on this, but since I have it all apart why not get it right. By moving it back like you did it will be a real tight fit, and I will confirm the rumors I like that.

BTW, how did the move of your business go?

Witzend · Nov 5, 2011

I'm mostly moved, but working a temp position at Wabtec (railway electronics) to stay cash flow neutral until I retire.
Note, by spacing the Sachs off the old plate it will make the assembly fatter, will you still be able to fit it through the opening in the bell housing to re-install?

rpwillia · Nov 5, 2011

Witzend said:
I'm mostly moved, but working a temp position at Wabtec (railway electronics) to stay cash flow neutral until I retire.
Note, by spacing the Sachs off the old plate it will make the assembly fatter, will you still be able to fit it through the opening in the bell housing to re-install?

Glad to hear work is working out. Yes, with the old plate it should all fit with no problem. I was actually pretty surprise when I loosened the last bolt as how the whole thing pretty much dropped out on its own. Plenty of space.

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