Okay, who can settle this question for us? Should the transmission be in neutral and the prop alpwed to freewheel on an inboard diesel ( and if so can it hurt the transmission) or should it be locked in reverse to prevent spinning but creating drag?
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Yanmar GM transmission answer
Link is to photo forum article explaining why GM transmission should be placed in reverse when sailing. May not be applicable to other manufacturers
Link is to photo forum article explaining why GM transmission should be placed in reverse when sailing. May not be applicable to other manufacturers
Not on my boat
Ken, If I leave my transmission in neutral and the prop begins to freewheel very fast, it will vibrate the shaft like crazy. So regardless of what the conventional wisdom says, there is no way my drive train is going to be allowed to vibrate like that. I had the system checked twice with both saying my drive train and bearings were lined up and in perfect shape. My system says..... Lock the prop! Ward
Ken, If I leave my transmission in neutral and the prop begins to freewheel very fast, it will vibrate the shaft like crazy. So regardless of what the conventional wisdom says, there is no way my drive train is going to be allowed to vibrate like that. I had the system checked twice with both saying my drive train and bearings were lined up and in perfect shape. My system says..... Lock the prop! Ward
agree--reverse is correct
Went to Strickly Sail in Chicago and asked the Yanmar rep the same question and got the same answer. Put it in reverse. You could harm the engine if the prop is allowed to rotate without adequate lubrication. Shifting to neutral is alittle hard when there is stress on the prop so be careful when you need to put it back into neutral when starting the engine.
Went to Strickly Sail in Chicago and asked the Yanmar rep the same question and got the same answer. Put it in reverse. You could harm the engine if the prop is allowed to rotate without adequate lubrication. Shifting to neutral is alittle hard when there is stress on the prop so be careful when you need to put it back into neutral when starting the engine.
Drag is not what you'd think!
The stopped prop, even a 3 blader, is less drag than a windmilling one. Seems strange, but true. The windmilling prop is generating lift (opposite to the lift when being driven by the engine) and that requires inducing drag to turn the prop, trans, and overcome the shaft log and seals. Most trannys have a oil pump attached to the output shaft to lube the trans when shaft is turning (no matter what is turning it), and the ones that do not have this type of arrangement are the ones that strongly suggest not to allow the freewheeling prop. The method of locking the prop underway while sailing varies by manufacturer. The drag from a stopped 3 blader can be pretty ugly, but will always be less than rotating.
The stopped prop, even a 3 blader, is less drag than a windmilling one. Seems strange, but true. The windmilling prop is generating lift (opposite to the lift when being driven by the engine) and that requires inducing drag to turn the prop, trans, and overcome the shaft log and seals. Most trannys have a oil pump attached to the output shaft to lube the trans when shaft is turning (no matter what is turning it), and the ones that do not have this type of arrangement are the ones that strongly suggest not to allow the freewheeling prop. The method of locking the prop underway while sailing varies by manufacturer. The drag from a stopped 3 blader can be pretty ugly, but will always be less than rotating.
But....
... none of this would be an issue if you used a folding or feathering prop. Once folded or feathered the prop remains stationary with the added benefit of very low drag. And additionally if the feathered prop is kept inline with the keel and rudder it creates the lowest possible drag. Having a fixed 3 down there is equal to dragging a bucket whether it's turning or not.
... none of this would be an issue if you used a folding or feathering prop. Once folded or feathered the prop remains stationary with the added benefit of very low drag. And additionally if the feathered prop is kept inline with the keel and rudder it creates the lowest possible drag. Having a fixed 3 down there is equal to dragging a bucket whether it's turning or not.
Depends on transmission and the manufacturer
But in most cases you want to keep the prop from spinning. So the theory is that if its in forward it would start to turn the clutch plates in the tranny when sailing at a good speed , but obviously the engine wouldn't turn over, thus you'd start to wear out or "glaze" over the clutch plates. But depending on the transmission type letting it free wheel supposedly is ok for certain types. For instance the HBW-100 Hurth Tranny manual says to leave it in nuetral. (Go to very bottom of page) http://www.marinedieseldirect.com/universal/200157/universal-owners-hurth-transmission.html
But in most cases you want to keep the prop from spinning. So the theory is that if its in forward it would start to turn the clutch plates in the tranny when sailing at a good speed , but obviously the engine wouldn't turn over, thus you'd start to wear out or "glaze" over the clutch plates. But depending on the transmission type letting it free wheel supposedly is ok for certain types. For instance the HBW-100 Hurth Tranny manual says to leave it in nuetral. (Go to very bottom of page) http://www.marinedieseldirect.com/universal/200157/universal-owners-hurth-transmission.html
Universal M - 12
The original manual for our '89 Oday 272LE with the Universal, says on page 8 in Bold, capitalized and underlined print: DO NOT LEAVE IN FORWARD DURING SAILING WITH ENGINE OFF. There must be a valid reason for this.
The original manual for our '89 Oday 272LE with the Universal, says on page 8 in Bold, capitalized and underlined print: DO NOT LEAVE IN FORWARD DURING SAILING WITH ENGINE OFF. There must be a valid reason for this.
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