I have been told that you should put the transmission in reverse when sailing. I was wondering why. What would happen if I let the trans in neutral and let the prop spin. This seems like a good idea to reduce drag. Any thoughts?
- Status
- Not open for further replies.
D
Dakota Jim Russell
Quite Thre Reverse
Pun intended. Spinning actually will increase your drag, not reduce it. If a helicopter is going to crash, the spinning the blades will reduce the descent some. I suppose I will get some flack for the above statement, so another reference would be the spinning oak leaf. Okay that didn't help,<grin>, oh well then consider my last paragraph: If you're concerned about reducing the drag, consider a feathering prop such as the maxi-prop. They are well worth it. I have one and love it.
Pun intended. Spinning actually will increase your drag, not reduce it. If a helicopter is going to crash, the spinning the blades will reduce the descent some. I suppose I will get some flack for the above statement, so another reference would be the spinning oak leaf. Okay that didn't help,<grin>, oh well then consider my last paragraph: If you're concerned about reducing the drag, consider a feathering prop such as the maxi-prop. They are well worth it. I have one and love it.
K
Ken Palmer
Wear and tear
The Yanmar maintenance class I attended said that in forward, you are putting more wear and tear on the transmission. In neutral, you are putting more wear and tear on the cutlass bearing and stuffing box. In reverse, wear and tear is a minimum. Ken Palmer, S/V Liberty
The Yanmar maintenance class I attended said that in forward, you are putting more wear and tear on the transmission. In neutral, you are putting more wear and tear on the cutlass bearing and stuffing box. In reverse, wear and tear is a minimum. Ken Palmer, S/V Liberty
T
Terry Arnold
Where's the wear and tear?
I have been puzzled by the continuing discussion about neutral, forward, or reverse positions as being associated with wear on the transmission. The following seems to me to be true. "It can make no difference whether the gear selector is in forward or reverse while sailing as long as the propeller shaft does not turn in the selected position since any wear on the transmission (or propeller shaft for that matter) must absolutely be associated with the shaft turning." What about it?
I have been puzzled by the continuing discussion about neutral, forward, or reverse positions as being associated with wear on the transmission. The following seems to me to be true. "It can make no difference whether the gear selector is in forward or reverse while sailing as long as the propeller shaft does not turn in the selected position since any wear on the transmission (or propeller shaft for that matter) must absolutely be associated with the shaft turning." What about it?
G
Gordon Myers
Location of "Wear & Tear"
A fix pitch prop - In neutral, if sailing with enough force (speed), the water pressure going over or around the prop will cause it to turn, therfore the drive shaft, ect. turning with out the engine providing lubrication. The amount of speed will depend on the amount of resistance the prop, driveshaft, engine ect. create. On my 42 it is about 2.5 to 3 kts. The same thing would happen if anchored in a current with enough speed. This turning of the drive shaft causes lots of wear & tear. By putting the transmission in reverse the prop can not turn unless you have figured out how to sail in reverse. Even folding or feathering props can spin until they fold or feather, therfore the transmissions should also be put in revese when sailing or anchoring in a current.
A fix pitch prop - In neutral, if sailing with enough force (speed), the water pressure going over or around the prop will cause it to turn, therfore the drive shaft, ect. turning with out the engine providing lubrication. The amount of speed will depend on the amount of resistance the prop, driveshaft, engine ect. create. On my 42 it is about 2.5 to 3 kts. The same thing would happen if anchored in a current with enough speed. This turning of the drive shaft causes lots of wear & tear. By putting the transmission in reverse the prop can not turn unless you have figured out how to sail in reverse. Even folding or feathering props can spin until they fold or feather, therfore the transmissions should also be put in revese when sailing or anchoring in a current.
G
Gene Barton, s/v Paradigm
Reverse Prop
Terry, you're partly right. But just as your car coasts (forward) when in forward, so does the prop. That is, the prop will not spin when left in reverse, but will freewheel when in forward. It will not spin backwards when locked in forward, and will not spin forward when locked in reverse. Despite what it seems, letting the prop spin when sailing does not reduce drag as well as locking it (in reverse). I know it seems like it should, but tests have shown it doesn't, and the physics involved having to do with cavitation, laminar flow, and other arcane fluid dymaics theory is too much to go into here. Just look up any scientific book on the subject, and they'll ALL tell you the same thing. Look in the archives - this topic has been beaten to death. Lock the prop (in reverse) or get a feathering one. Reducing wear on the moving parts, though is actually an even better reason, since the drag introduced by a propeller, stationary or spinning, is so small. I don't agonize over propeller drag if my boat bottom is covered with barnacles and seaweed!
Terry, you're partly right. But just as your car coasts (forward) when in forward, so does the prop. That is, the prop will not spin when left in reverse, but will freewheel when in forward. It will not spin backwards when locked in forward, and will not spin forward when locked in reverse. Despite what it seems, letting the prop spin when sailing does not reduce drag as well as locking it (in reverse). I know it seems like it should, but tests have shown it doesn't, and the physics involved having to do with cavitation, laminar flow, and other arcane fluid dymaics theory is too much to go into here. Just look up any scientific book on the subject, and they'll ALL tell you the same thing. Look in the archives - this topic has been beaten to death. Lock the prop (in reverse) or get a feathering one. Reducing wear on the moving parts, though is actually an even better reason, since the drag introduced by a propeller, stationary or spinning, is so small. I don't agonize over propeller drag if my boat bottom is covered with barnacles and seaweed!
A
Andy Falls
Really Lock the #%$^ prop
If you guys are really worried about what is the best way to lock (or not lock the prop), why haven't you considered the prop locking device sold in marine stores? Or be real cheap and lock the vice grips on the shaft! (ha ha but I've seen it done!) Sooo, has anyone installed a proplock thinging mebob?
If you guys are really worried about what is the best way to lock (or not lock the prop), why haven't you considered the prop locking device sold in marine stores? Or be real cheap and lock the vice grips on the shaft! (ha ha but I've seen it done!) Sooo, has anyone installed a proplock thinging mebob?
T
Terry Arnold
much ado
propeller shaft does not move when in gear, ----any gear---- unless the engine is running. period. IF anyone's shaft does turn while in gear then so does the engine, which should be fairly easy to check or else the clutch will be shortly destroyed.
propeller shaft does not move when in gear, ----any gear---- unless the engine is running. period. IF anyone's shaft does turn while in gear then so does the engine, which should be fairly easy to check or else the clutch will be shortly destroyed.
A
Alex
The shaft do turn if left in forward gear..
.. if your engine is 2GM20F Yanmar (like most Hunters in this size range), and it should .Only reverse will lock it. Indeed if left in neutral , the spin of propeller while sailing will slow down the boat more than if locked , additional to whatever wear and tear it cause to engine . External shaft lock device are good , but unpractical on these boats where there is not enough exposed lenght of shaft for it, like my '29.5' . This one also has not enough clearance (up and down)even for basic flexible shaft-gear coupling device (which cold dampen a lot of vibrations on small engines) , not to speak of more advanced 'Aquadrive systems' and alike ,which are real healty on dampening vibration and canceling misalignment faults. I hope in later boats -and bigger- there was room left for such devices.
.. if your engine is 2GM20F Yanmar (like most Hunters in this size range), and it should .Only reverse will lock it. Indeed if left in neutral , the spin of propeller while sailing will slow down the boat more than if locked , additional to whatever wear and tear it cause to engine . External shaft lock device are good , but unpractical on these boats where there is not enough exposed lenght of shaft for it, like my '29.5' . This one also has not enough clearance (up and down)even for basic flexible shaft-gear coupling device (which cold dampen a lot of vibrations on small engines) , not to speak of more advanced 'Aquadrive systems' and alike ,which are real healty on dampening vibration and canceling misalignment faults. I hope in later boats -and bigger- there was room left for such devices.
M
Michael Cohn
Enough
I think this topic has been beaten to death as much as the mainsail furling thing... From what I can tell: 1. Freewheeling is bad. 2. Forward may or may not be OK. 3. Reverse is OK. Also - exactly WHAT clutch are people referring to? The only one I have is in my car - there is no clutch in my boat at all, just an engine, a coupler, and a trans. MC
I think this topic has been beaten to death as much as the mainsail furling thing... From what I can tell: 1. Freewheeling is bad. 2. Forward may or may not be OK. 3. Reverse is OK. Also - exactly WHAT clutch are people referring to? The only one I have is in my car - there is no clutch in my boat at all, just an engine, a coupler, and a trans. MC
W
Wilkie Marvel
Lock the Prop
I always lock my prop... If you have a solid prop suggest you mark the shaft where you can look at it so the prop blades are vertical behind the keel.. This will give you less drag..
I always lock my prop... If you have a solid prop suggest you mark the shaft where you can look at it so the prop blades are vertical behind the keel.. This will give you less drag..
K
Ken Palmer
Re: Enough
I found my student handbook from the Yanmar class I attended a couple years ago. Unfortunately, there was no explanation of the operation of the transmission. I do remember the instructor explaining how it works: There is a "clutch" device that slides forward or back on the shaft, depending on your "gear" lever placement. If the lever is in forward position when sailing, there is constant friction between the "clutch" and the drive part (sorry, I am having an old age moment, and cannot remember exactly). My notes said there are three choices: 1) put in reverse (preferred). 2) put in neutral (OK, but spinning prop causes drag and wear). 3) put in forward (never, never, never... that is what the mechanic said). Of course, everybody has their own opinion and experiences. I agree, this subject is being talked to death. Us sailors locked in by winter are just counting down the days until spring, and are looking for things to talk about. The groundhog said 6 more weeks! Please hurry! Ken Palmer, S/V Liberty
I found my student handbook from the Yanmar class I attended a couple years ago. Unfortunately, there was no explanation of the operation of the transmission. I do remember the instructor explaining how it works: There is a "clutch" device that slides forward or back on the shaft, depending on your "gear" lever placement. If the lever is in forward position when sailing, there is constant friction between the "clutch" and the drive part (sorry, I am having an old age moment, and cannot remember exactly). My notes said there are three choices: 1) put in reverse (preferred). 2) put in neutral (OK, but spinning prop causes drag and wear). 3) put in forward (never, never, never... that is what the mechanic said). Of course, everybody has their own opinion and experiences. I agree, this subject is being talked to death. Us sailors locked in by winter are just counting down the days until spring, and are looking for things to talk about. The groundhog said 6 more weeks! Please hurry! Ken Palmer, S/V Liberty
T
Terry Arnold
Much Ado Two
The thread on locking the prop while sailing includes a variety of opinions. Yesterday, I took out the engine manual and after studying it conclude that those who recommend sailing in revese are right and that those who recommend other things (like my earlier post) are wrong. In an attempt to make amends for my earlier misinformation, I have posted a photo forum article which may be more than anyone wants to know about the 1GM 2GM 3GM transmission. At least remember this. For the good of your transmission: SAIL IN REVERSE.
The thread on locking the prop while sailing includes a variety of opinions. Yesterday, I took out the engine manual and after studying it conclude that those who recommend sailing in revese are right and that those who recommend other things (like my earlier post) are wrong. In an attempt to make amends for my earlier misinformation, I have posted a photo forum article which may be more than anyone wants to know about the 1GM 2GM 3GM transmission. At least remember this. For the good of your transmission: SAIL IN REVERSE.
B
Bob E.
That should settle it
Very convincing. Excellent post. That should settle the discussion, except that now we'll probably hear from the people who can't get the transmission out of reverse to start the engine because they don't know to slow down before shifting. That "servo locking" effect can be strong. <g>
Very convincing. Excellent post. That should settle the discussion, except that now we'll probably hear from the people who can't get the transmission out of reverse to start the engine because they don't know to slow down before shifting. That "servo locking" effect can be strong. <g>
M
Mickey McHugh
Bob's right
about questions on how to start the engine when it will not shift back to neutral. On my H40.5 which has a 50 HP Volvo I have to SLOW down (< 3 knots), turn the key to start the engine, quickly shift to neutral, raise the shift disconnect, give it some trottle to keep the charging alarm from going off (volt meter goes up to 14VDC), shift back to neutral and then shift as required. The Volvo will give a charging alarm if it does not have enough RPMs when it first starts. While sailing, it's good to know that if I need reverse in a hurry I just have to hit the key and I am slowing down! Can someone with a Yanmar give us the start from locked procedure?
about questions on how to start the engine when it will not shift back to neutral. On my H40.5 which has a 50 HP Volvo I have to SLOW down (< 3 knots), turn the key to start the engine, quickly shift to neutral, raise the shift disconnect, give it some trottle to keep the charging alarm from going off (volt meter goes up to 14VDC), shift back to neutral and then shift as required. The Volvo will give a charging alarm if it does not have enough RPMs when it first starts. While sailing, it's good to know that if I need reverse in a hurry I just have to hit the key and I am slowing down! Can someone with a Yanmar give us the start from locked procedure?
G
Guest
B
Bryan
Starting in reverse is safe?
Are you guys sure that starting your motor in reverse while underway is a safe procedure? Seems like it would put a lot of strain on the motor and transmission.
Are you guys sure that starting your motor in reverse while underway is a safe procedure? Seems like it would put a lot of strain on the motor and transmission.
B
Bob E.
Reverse starting
To start the Yanmar in reverse, just turn the key and push the start button. However, I wouldn't do it while underway, except in an emergency. The strain on the transmission and engine would be minor compared to normal operating forces, but I would really worry about the starter motor and gear. I doubt these are designed to take that kind of strain, and overheating the starter motor's coils could happen quickly.
To start the Yanmar in reverse, just turn the key and push the start button. However, I wouldn't do it while underway, except in an emergency. The strain on the transmission and engine would be minor compared to normal operating forces, but I would really worry about the starter motor and gear. I doubt these are designed to take that kind of strain, and overheating the starter motor's coils could happen quickly.
M
Mike DiMario
Soon Shafted!
To all it may concern, It is not difficult to conclude that starting your marine engine while in reverse can be a shock to the system. If you take it nice and easy, the transmission can be shifted into neutral prior to starting. This is provided you take it nice and easy when you shut it down. Although I think you can get away with starting in reverse, it sounds like he2xl and vibrates to high heaven. My advice is to avoid it if possible, unless you engine starts without the shock. Mike D.
To all it may concern, It is not difficult to conclude that starting your marine engine while in reverse can be a shock to the system. If you take it nice and easy, the transmission can be shifted into neutral prior to starting. This is provided you take it nice and easy when you shut it down. Although I think you can get away with starting in reverse, it sounds like he2xl and vibrates to high heaven. My advice is to avoid it if possible, unless you engine starts without the shock. Mike D.
M
Michael Cohn
WHY???
Why in the world would anyone want to start their engine in reverse?? All you have to do to shift from reverse to neutral when sailing is head up a bit and slow the boat down, or luff the sails if you prefer this method. Anyone who gets into an "emergency" where the engine needs to be started in reverse is clearly not thinking ahead. MC
Why in the world would anyone want to start their engine in reverse?? All you have to do to shift from reverse to neutral when sailing is head up a bit and slow the boat down, or luff the sails if you prefer this method. Anyone who gets into an "emergency" where the engine needs to be started in reverse is clearly not thinking ahead. MC
- Status
- Not open for further replies.