FigBug

Does this look like a lot of wear for 1200 hours?

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looks like its been ridden hard and put away wet , not had a great deal of love .

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It shouldn't look that bad at 12000 hours.

That thing is beat to shit.

At 1200 hours it should look new. By comparison, in a car 1200 hours equates to about 30,000 miles.

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There's something else going on there, I imagine the springs were a bit loose and it started chattering, then chewed itself apart. As it wears the clearances get bigger and it gets worse and worse. I've never seen one that bad though.

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I had a Universal M-30 that did exactly that to the damper. Crummy Universal parts? Running in neutral for charging? Resonance with the gearbox input shaft? Who knows?

That is not right.

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The boat was owned by a sailing school, now it's owned by a co-op. So lots of different skippers, probably not a lot of love. But still, seems in really bad shape.

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Maybe a lot of gear changes at non-idle RPM by anxious students or co-op members that are doing the same during docking.

But still...its a ton of wear on a part that usually lasts the life of the engine. Maybe 1 replacement in 3000 or 4000 hours would be my guess as more typical. 

Is it a Universal part or a reputable 3rd party maker of damper plates?

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That looks like there's a serious torsional vibration problem with far more energy than that plate can absorb. I'd look for problems with the prop keyway and/or a loose coupling and/or worn splines. The real challenge is discerning the problem from the symptom; the whole drive line is suspect.

Couple of questions that might help - what's the boat, what's the prop, what's the diameter of the prop shaft and how long is the shaft?

 

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It's a 1976 Catalina 30. I'll need to look up / measure to get the answers to your other questions.

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An oversized prop usually isn't the problem as it creates lots of resistance and can absorb quite a bit of vibration. It's more likely that an undersized prop caused the torsional reversals that cause the kind of damage shown.

Although it could just as easily be that the prop hit something that destroyed the dampener and that it's not a vibration problem at all.

What led to taking it all apart and finding that mess?

 

 

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The propellor is a 13RH9.

The damper plate failed when reducing throttle when approaching dock. Throttled back up and there was no thrust.

Would hitting something do all that damage at once? Or would hitting something throw the drive train out of balance which causes everything to wear? i.e. should I still be checking for a bent propellor, drive shaft etc?

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Sure looks like long-term wear to me. Mine looked exactly like yours, but was still functioning when removed. Might have been triggered long ago by some event. The damper plate is under the most duress when in neutral or when prop loads are very small....like motor sailing. You must have heard the rattling for a long time. A rattle which would smooth out under higher load or higher RPM? I heard it, but grossly underestimated the damage being done.

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In neutral? I doubt there's much torsional vibration when the engine is spinning only the transmissions input shaft. The engine may vibrating around, but that's all on the mounts and the flange, not torsionally down the drive train.

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48 minutes ago, Moonduster said:

In neutral? I doubt there's much torsional vibration when the engine is spinning only the transmissions input shaft. The engine may vibrating around, but that's all on the mounts and the flange, not torsionally down the drive train.

Yeah, in neutral. Why your doubt? The engine certainly produces torsional vibration...being a diesel with a finite number of cylinders and minimal flywheel. The unloaded input shaft of the transmission is free to bang around. That reflects the energy back towards the engine. The unloaded springs are all liability in that condition. It is a resonance thing. With much energy pumping it. Very common mechanical issue. Even my drill press does it until the bit engages the work piece.

Load the system up, or change the excitation frequency and the problem is often solved. All the parts stay in contact rather than hammering at each other. The energy goes someplace besides destroying the damper plate. You’re an engineer, right? So you know all about this stuff.

Certainly we have very little precise info about the OP’s situation, however I reply because I had the exact same issue. On a Universal engine even. I know precisely what I did to cause it: long term low RPM running in neutral with a slowly increasing rattle noise.

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Left in forward while sailing so the clutch is always slipping while happily sailing around?

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The freewheeling might cause havoc in the transmission, but it shouldn't affect the dampener plate at all.

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Is it possible to install the damper backwards? I see striated wear marks on the sides of the springs (which is never good), and the springs have pushed back-and-forth into their retainers. If someone installed it backwards, the springs might have rubbed and then been beaten. I don't know much about real boat engines, but when I upgraded my 1968 Ford to a TKO 5 speed, I had to hunt for a very specific offset clutch disk. Other people were using Chevy clutch disks which fit but disintegrated because the disk springs hit the flywheel. 

Snubs

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Cannot easily install backwards because the little retaining screws are only on flywheel side. The springs got damaged after moving out of position in the slots...presumably...perhaps rolling around in the bell housing? Must have been noisy!

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On 8/13/2019 at 12:23 AM, El Boracho said:

Yeah, in neutral. Why your doubt? The engine certainly produces torsional vibration...being a diesel with a finite number of cylinders and minimal flywheel. The unloaded input shaft of the transmission is free to bang around. That reflects the energy back towards the engine. The unloaded springs are all liability in that condition. It is a resonance thing. With much energy pumping it. Very common mechanical issue. Even my drill press does it until the bit engages the work piece.

Load the system up, or change the excitation frequency and the problem is often solved. All the parts stay in contact rather than hammering at each other. The energy goes someplace besides destroying the damper plate. You’re an engineer, right? So you know all about this stuff.

Certainly we have very little precise info about the OP’s situation, however I reply because I had the exact same issue. On a Universal engine even. I know precisely what I did to cause it: long term low RPM running in neutral with a slowly increasing rattle noise.

You forget who you are talking to. 

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