Driveline vibration when engine is off - SailNet Community
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post #1 of 16 Old 04-21-2016 Thread Starter
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Driveline vibration when engine is off

Sailed my new-to-me 1988 PSC34 for the first time over the past couple days in some pretty good wind. When the boat accelerates through six knots or so under sail, you can see the engine tremble as the prop really gets spinning. (Engine off, transmission in neutral) Probably less than a quarter inch of displacement twice per second. When the boat slows back down due to less wind or eased sheets, the vibration stops and the prop just makes it's quiet "thump-thump" noise. The prop is an 18-inch two-blade job that's freshly balanced. Thoughts?
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post #2 of 16 Old 04-21-2016
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Re: Driveline vibration when engine is off

Pull your engine into reverse gear to stop the prop "freewheeling". (Alternately, you can add a shaft lock but that's rather more effort than really necessary.)

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Re: Driveline vibration when engine is off

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Originally Posted by svHyLyte View Post
Pull your engine into reverse gear to stop the prop "freewheeling". (Alternately, you can add a shaft lock but that's rather more effort than really necessary.)
Yes... except that some manufacturers definitively say not to do so, so check.

Ron

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post #4 of 16 Old 04-21-2016
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Re: Driveline vibration when engine is off

It seems tha t a folding prop is desired here
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Re: Driveline vibration when engine is off

Really nice boat, I would check to see if there is a shaft break. Depending on the location of the engine/transmission. Different set ups look different. Some are like a box over the shaft, others are just basically a stick you put into a slot to hold the shaft in place. If you have a 2 blade prop it will likely line it up with the keel/rudder. Feathering/folding props are great but quite expensive, and can add a bit of complexity to the system.

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post #6 of 16 Old 04-21-2016 Thread Starter
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I found info that says Kanzaki gearboxes are to be left freewheeling.

I'm just curious if other PSC guys/gals have any vibration as I've described.
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Re: Driveline vibration when engine is off

Is is supposed to vibrate that much with a 2 blade prop? Maybe a 3 blade prop would do better.

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post #8 of 16 Old 04-22-2016
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Re: Driveline vibration when engine is off

We have a 3 blade max prop and when sailing I can noticeably hear and feel the prop spinning until I shift into reverse, feathering the prop. Assuming your engine alignment is good, then the noise and vibration you are feeling is probably normal.

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post #9 of 16 Old 04-22-2016
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The way to stop a Max Prop from free wheeling is to kill the engine while still motoring in forward. The forward motion of the boat feathers the blades. You can leave it in forward or put it in neutral. The prop should not be spinning, if it is, you've defeated the reason for buying a feathering prop.
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Re: Driveline vibration when engine is off

Quote:
Originally Posted by Davashcow View Post
I found info that says Kanzaki gearboxes are to be left freewheeling.

I'm just curious if other PSC guys/gals have any vibration as I've described.
We locked our Kanzaki transmission (on a 2GM20FW) in reverse to prevent freewheeling for 15 years without difficulty.

FWIW...

"It is not so much for its beauty that the sea makes a claim upon men's hearts, as for that subtle something, that quality of air, that emanation from the waves, that so wonderfully renews a weary spirit."
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