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Old 14-12-2020, 15:32   #1
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Lightbulb Boat Transmissions

Although I have been boating a long time and Enjoy my Sea Ray 30 weekender. I am trying to extend her reach. So on with my question If my prop spins backward with the motors off will that hurt my transmissions. If yes can something be done to prevent the damage.

I am looking into putting a Kite Sail on the front of my boat.
It looks like I can get 5 knots down wind with this rig.

Please any feedback will be appreciated
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Old 14-12-2020, 16:03   #2
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Re: Boat Transmissions

It depends on the transmission - some are hurt, others aren't.
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Old 14-12-2020, 16:19   #3
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Re: Boat Transmissions

If it a hydraulic transmission, the pump circulates oil that cools the rear bearing. Depending on the speed of the prop, it generates heat. That can damage the rear seal and on some, the bearings and clutch. Check the temp, but also ask the manufacturer.
If it's manual, I've never heard of one being damaged even turning fast.
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Old 14-12-2020, 16:26   #4
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Re: Boat Transmissions

You can simply lock down the shaft with a pipe wrench or a piece of chain if there is any doubt. A more involved remedy would be to install a thrust bearing somewhare along the shaft to transfer all thrust directly to the hull. Some transmissions can safely be placed in neutral with the shaft trailing. The manufacturer should be consulted or if this is not possible, then a competent small boat mechanic.
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Old 15-01-2021, 08:30   #5
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Re: Boat Transmissions

Wotname is correct. It depends on the transmission, but on some you can stop the shaft from turning my dropping the transmission into reverse.
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Old 16-01-2021, 05:00   #6
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Re: Boat Transmissions

If in doubt, you can stop the shaft turning with a bit of light line with a loop on one end. Snag one of the coupling bolts with the loop and make the line fast to something strong nearby.

Make the line light enough so that if you forget it or need the engine in a hurry it will snap without doing any damage to the shaft, coupling or bearings.

I used this setup for years without problems. (No longer needed thanks to my feathering kiwiprop.)
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