Dumb question, probably, but I recently replaced the entire drive train on my '87 H31: new cutlass bearing, shaft log, shaft, PYI dripless shaft seal, etc. Sailing in SFO I have plenty of wind most of the time, so I elected to change to a 3 bladed prop, and I didn't really care about the extra drag. The new prop works great, and engine vibration etc. is minimal when motoring, and the whole drive train rotates easily following the alighment, but I find that when under sail, with the engine shut off, the propeller windmills, creating a perceptible vibration, and since this didn't happen with the 2 bladed prop, it surprised me a bit, and I was wondering if this is a problem, and if so what to do about it.
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Rick, the engine is part of the drive train. Did
you replace that too? If it's still a Yanmar, put it in reverse when under sail. Simple, but drag? That's another issue.
you replace that too? If it's still a Yanmar, put it in reverse when under sail. Simple, but drag? That's another issue.
still the original engine...
Thanks for the hint... I tried leaving it in forward once, but it still was turning, and I thought that it might be bad for the tranny. I'll try it in reverse. Not a problem with the increased drag, as I can generally get hull speed with the wind in the Bay being what they are, especially in the summer.
Thanks for the hint... I tried leaving it in forward once, but it still was turning, and I thought that it might be bad for the tranny. I'll try it in reverse. Not a problem with the increased drag, as I can generally get hull speed with the wind in the Bay being what they are, especially in the summer.
Put it in reverse
Rick, There has been considerable discussion about the value of freewheeling (less drag) vs the wear on the transmission (no oil flow). In the end, I'm not sure there was a definitive answer, but I've always locked my prop by putting the transmission in reverse. As you say, the winds are generally enough on the Bay (except for this week) that you can handle the extra drag, and it should completely eliminate any vibration issues. - Richard S/V Discovery South Beach
Rick, There has been considerable discussion about the value of freewheeling (less drag) vs the wear on the transmission (no oil flow). In the end, I'm not sure there was a definitive answer, but I've always locked my prop by putting the transmission in reverse. As you say, the winds are generally enough on the Bay (except for this week) that you can handle the extra drag, and it should completely eliminate any vibration issues. - Richard S/V Discovery South Beach
Reverse
I own a Sparkman & Stephens designed Tartan 33. It has a Universal Diesel and Hurth transmission. The owners manual clearly states that you should place the transmission in reverse while sailing. That locks the prop so it does not spin. The free wheeling prop creates much more drag than one that is locked and does not spin while sailing. Think about it. That prop is spinning in the opposite direction than you are sailing. Suggest you check your owners manual either engine or boat and see if it tells you. Good luck.
I own a Sparkman & Stephens designed Tartan 33. It has a Universal Diesel and Hurth transmission. The owners manual clearly states that you should place the transmission in reverse while sailing. That locks the prop so it does not spin. The free wheeling prop creates much more drag than one that is locked and does not spin while sailing. Think about it. That prop is spinning in the opposite direction than you are sailing. Suggest you check your owners manual either engine or boat and see if it tells you. Good luck.
Spinning Prop
This has been beat to death in the archives. There IS a definitive answer: When you free-wheel, you're turning the transmission without any lubrication. All the experts and manuals say put the transmission in reverse. The drag is not significant, and we're talking about a cruising boat, after all.
This has been beat to death in the archives. There IS a definitive answer: When you free-wheel, you're turning the transmission without any lubrication. All the experts and manuals say put the transmission in reverse. The drag is not significant, and we're talking about a cruising boat, after all.
Tried it in reverse, but...
Thanks everyone... I tried it in reverse the other day, stopped the prop from spinning, but then I couldn't get the transmission into neutral under the reverse load. The shifter was just sort of jammed. I ended up starting it in reverse, while sailing forward, and was releived that it actually started with the additional load on the starter. Anyway, thanks for the input.
Thanks everyone... I tried it in reverse the other day, stopped the prop from spinning, but then I couldn't get the transmission into neutral under the reverse load. The shifter was just sort of jammed. I ended up starting it in reverse, while sailing forward, and was releived that it actually started with the additional load on the starter. Anyway, thanks for the input.
Rick,,,,
That's a hell of a prop you've got there. And you obviously have a Yanmar. Cone clutches behave that way. But don't fret. When you need the engine, come head to wind so as to slow down. That prop will help to do that too.
P.S. Actually, you had less load on the starter. The prop was trying to turn over the engine.
That's a hell of a prop you've got there. And you obviously have a Yanmar. Cone clutches behave that way. But don't fret. When you need the engine, come head to wind so as to slow down. That prop will help to do that too.
P.S. Actually, you had less load on the starter. The prop was trying to turn over the engine.One cup of coffee
Fred, I've only had one cup of coffee, but if the transmission is in reverse, wouldn't the force of the water while the boat is moving forward add load to the starting effort? I don't think that starting in reverse presents any real problem. Our 356 seems to shift out to neutral with the engine stopped pretty easy. For some reason, the 290 occasionally wants to stay in. In that event, we just start in reverse and then shift to neutral. Sometimes I start in reverse because I forget to check before starting the engine. So far, seems like no real problem. Dan Jonas (S/V Feije II)
Fred, I've only had one cup of coffee, but if the transmission is in reverse, wouldn't the force of the water while the boat is moving forward add load to the starting effort? I don't think that starting in reverse presents any real problem. Our 356 seems to shift out to neutral with the engine stopped pretty easy. For some reason, the 290 occasionally wants to stay in. In that event, we just start in reverse and then shift to neutral. Sometimes I start in reverse because I forget to check before starting the engine. So far, seems like no real problem. Dan Jonas (S/V Feije II)
Dan, Fred will tell you
he is right because he is. Fred will have to explain it, I don't want to step on his shoes. Scott
he is right because he is. Fred will have to explain it, I don't want to step on his shoes. Scott
I checked the archives and found out
Thanks again... I checked the archives and found a post from another guy who got the heebie jeebies when he couldn't shift out of reverse under sail. One reply was from a fellow who nudged the shifter into neutral as he hit the starter, and another from someone who just started in reverse. Either way, now I know I won't get stuck in reverse, unable to start the engine, and driven helplessly by the tide deep into the Pacific. Thanks again.
Thanks again... I checked the archives and found a post from another guy who got the heebie jeebies when he couldn't shift out of reverse under sail. One reply was from a fellow who nudged the shifter into neutral as he hit the starter, and another from someone who just started in reverse. Either way, now I know I won't get stuck in reverse, unable to start the engine, and driven helplessly by the tide deep into the Pacific. Thanks again.
Dan's right
A windmilling prop with the boat going forward turns in the same direction as the prop turns when in forward with the engine running. With the engine in reverse and the boat sailing, the prop still wants to turn in the forward direction and since the boat is in reverse, if the prop actually turned the engine, it would be turning backward. Thus with the starter engaged in reverse, the prop must be turned in a direction opposite to that of the windmilling tendency, increasing not decreasing the load on the starter.
A windmilling prop with the boat going forward turns in the same direction as the prop turns when in forward with the engine running. With the engine in reverse and the boat sailing, the prop still wants to turn in the forward direction and since the boat is in reverse, if the prop actually turned the engine, it would be turning backward. Thus with the starter engaged in reverse, the prop must be turned in a direction opposite to that of the windmilling tendency, increasing not decreasing the load on the starter.
OK, look at the time of that post of mine this
morning. Not once have I claimed to be a morning person. And I hadn't set up my coffee IV yet. The prop effect is the other way around. It's afternoon now and all so clear. I'm feeling much better.
morning. Not once have I claimed to be a morning person. And I hadn't set up my coffee IV yet. The prop effect is the other way around. It's afternoon now and all so clear. I'm feeling much better.
Thank goodness...
I'm glad the rotational torque question was finally solved, because I thought my head would explode if I thought about it any more.... I'm pretty OK with counter-intuitive answers being correct, as with a lot of quantum physics and things like that, well, you just have to believe it or not, eh? But the prop torque on the starter in reverse thing, well, it was getting to me, I started drinking transmission fluid, but that didn't help. I'm glad that for once, the intuitive answer was right. At this point, intuition is pretty much all I have left to count on, as faulty as it is. I never actually do the math, these days; I just let the smart guys do it, and then they tell me the answer. Fair winds, cool sunsets and following seas to all. Thanks again - Rick
I'm glad the rotational torque question was finally solved, because I thought my head would explode if I thought about it any more.... I'm pretty OK with counter-intuitive answers being correct, as with a lot of quantum physics and things like that, well, you just have to believe it or not, eh? But the prop torque on the starter in reverse thing, well, it was getting to me, I started drinking transmission fluid, but that didn't help. I'm glad that for once, the intuitive answer was right. At this point, intuition is pretty much all I have left to count on, as faulty as it is. I never actually do the math, these days; I just let the smart guys do it, and then they tell me the answer. Fair winds, cool sunsets and following seas to all. Thanks again - Rick
My Gawd Rick,
You're into Quantum Mechanics!!?? My wife works for 911, I'll get help started for you, right away. Stay calm, drink plenty of fluids, preferably vodka.
You're into Quantum Mechanics!!?? My wife works for 911, I'll get help started for you, right away. Stay calm, drink plenty of fluids, preferably vodka.
Terry, Dan, and Fred are you sure
prop will windmill in neutral the same direction with the boat moving forward as it would in forward gear with engine engaged, in other words clockwise when viewed from behind prop on most boats? Scott
prop will windmill in neutral the same direction with the boat moving forward as it would in forward gear with engine engaged, in other words clockwise when viewed from behind prop on most boats? Scott
Not wrong very often
Fred, Early or not, you don't miss it very often. I'm not a morning person either, so even at 10:00 am I had to think about it for a minute. Dan Jonas (S/V Feije II)
Fred, Early or not, you don't miss it very often. I'm not a morning person either, so even at 10:00 am I had to think about it for a minute. Dan Jonas (S/V Feije II)
Thanks Dan, I try, and learned one trick that
helps a lot as a police officer. Keep my mouth shut when I don't know nutn'.
helps a lot as a police officer. Keep my mouth shut when I don't know nutn'.
Dan, my head hurts
So I am motoring along at 6 knts, shift to neutral, and the prop starts to windmill (just assume it does)because it takes my boat a long time to drop speed (just assume again). Are you saying the prop is turning the same direction during both events? Scott
So I am motoring along at 6 knts, shift to neutral, and the prop starts to windmill (just assume it does)because it takes my boat a long time to drop speed (just assume again). Are you saying the prop is turning the same direction during both events? Scott
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