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damper plate 411

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have a 35 year old Westerbeke that runs like a top in my boat that I am getting ready to start using for cruises.

Most the systems have been renewed in last couple of years.


One area I know little about is damper plates.

When do you replace one?

Do they warn you when they are getting to end of life, or is it you just cannot get power?

Seeing some aftermarket versions use oil resistant polymers instead of springs. Are they any better?

Worth the aggravation to just replace it during the off season for peace of mind?

Any tricks to aid is swapping one out?


Thanks in advance for any advice

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Damper plate does not have much to do with power. They are replaced when they look worn or make noise. I would replace anytime the transmission is removed, certainly. They wear out faster at low power settings and in neutral...like battery charging.

Very easy to replace if you are already “in there”.

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They do wear out and they're not difficult to replace. Remove the transmission, unbolt the plate, bolt up the new one and replace the transmission. Easy as can be - provided you can remove the coupling and transmission!

Choosing the right dampener isn't trivial and the benefits of the right dampener cannot be believed until one finds it. The purpose of the plate is to dampen torsional vibration, which occurs because, for example, a 4-cycle 4-cylinder diesel has two power strokes per revolution and these create impulses of rotation, not the smooth rotation that we imagine. The engine, spline, transmission, coupling, shaft and propeller all absorb some of this energy pulse and then release it causing a twisting effect. In extreme cases, the shaft experiences reversal and this leads to the horrendous chattering some boats experience at a specific (usually low) RPM.

There are dozens of kinds of dampeners from the usual spring arrangement to fairly complex torque activated variable dampeners. Don't assume that the "stock" plate does the right thing, especially if you've got a long prop shaft that's at the skinny end of acceptable diameter.

For most boats, paying for a Torsional Vibration Analysis doesn't make sense, but talking to a competent marine diesel shop does. Modern plates cover a fairly wide range of torque and a simple upgrade can do wonders to reduce engine vibration and noise.


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