Systems+Engines

To Freewheel or Not

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Edward Simon of Orchard Park, New York asks:

I sail an S2 8.7 with a Yanmar 2GM engine. When sailing, should the prop be locked or should I let it freewheel? If I should lock it, is it better to put the transmission in forward or reverse? I have asked around the boatyard and have received conflicting answers.

Nigel Calder replies:

There are several different issues here: drag, noise and wear. I’ll ignore the controversial question of drag, because I assume you don’t want to listen to the annoying rumble of a freewheeling propeller if you don’t have to. You also won’t want the unnecessary transmission and bearing wear.

Yours is a manual transmission (as is the case on most sailboats), and it should be locked by putting it in reverse. If you put it in forward gear, under certain sailing conditions you can get clutch slip and wear. Some boats have hydraulic transmissions, which should not be allowed to freewheel, since there is no lubrication and failure is a possibility. These, however, cannot be locked by putting them in gear, but rather require the use of a shaft brake.

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