Does it hurt to freewheel prop?

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Dale Young

I believe that it was M.i.t. that did a drag study that found that a freewheeled prop (during sail) greatly reduced drag throughout the speed range of a given vessel. I have a 2qm15 with the standard transmission but, I have no idea if the transmission can receive lubrication during freewheeling. It seems as though it does,since it isn't a pressured system. any advice is appreciated.
 
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Warren Blanchard

Freewheeling Prop

Funny you should ask...there was a letter in the 01/15 issue of Practical Sailor which I think pretty much reflects the conventional wisdom on the subject. Here it is: Freewheeling Prop Re: the recent correspondence on prop drag and freewheeling (November 1, 2000). Surely the answer is straightforward. If you have a pressure-lubricated gear box (I believe Borg Warner for instance) under no circumstances freewheel as there will be no oil flow to the box. Hurth, one of the commonest boxes fitted to sailing boats and above all to Perkins/Westerbeke, definitely advises against freewheeling and goes as far as to suggest always engaging the reverse gear to hold the shaft. Reason: Lack of proper splash lubrication to the plates, which wear quickly if badly lubricated with ATF fluid. Unpressurized splash lubricated bevel gear boxes can probably freewheel safely. Patrick Matthiesen London, England Hope this sheds some light on your question. There was also a PS Advisor in a past issue that talked about it. If I can find it, I'll pass it on. Warren Blanchard
 
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Bryan C.

The long debate

The issue of whether to lock or freewheel props has been debated here on the HOW for years. I think the general consensus among those who have researched the issue is that the gear should be locked in reverse to prevent damage to the tranny.
 
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Gordon Torresen

Freewheeling

The reversing gear on the 2QM15 can freewheel if you choose. The splash lubrication is working well even if no gears are turning. The clutch cage spins with the output shaft (now being spun by the propeller), is in the lube oil, and looks and functions like a paddle wheel. The letter from Practical Sailor is an uninformed opinion. Just because they print it doesn't make it right. Although there are some reversing gears that will be harmed by free wheeling, the Hurth style is not among them. As I recall the results of the drag studies, there wasn't a great deal of difference, either way. I think I would just pop it into reverse, eliminating the noise and saving wear on the oil seals.
 
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