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Old 28-11-2013, 08:13   #1
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Prop Spinning under Sail?

Anybody else out there own a 1980 Cal 39? We bought one about 18 months ago and we love it, but I'm perplexed.

I've always understood that when under sail it's best to put the engine in reverse to prevent the prop & shaft from spinning when the oil pump is not running to provide lubrication.

On our boat, which has a Perkins 4-108 engine with a 3-bladed prop, it doesn't matter whether we have the engine in neutral, forward or reverse, we can hear the prop spinning when we're under sail, even in relatively light wind.

Every instinct I have shouts "This can't be good!" But is it normal for one of these? If not, what do we do?

Does anyone have any thoughts or advice? You can answer here or e-mail me directly at BackYardMapleVT@Hotmail.com.

Thanks!
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Old 28-11-2013, 13:09   #2
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Re: Prop spinning under sail ???

The transmission is the key in the answer to your question. If it is a Velvet Drive its ok to let it spin. If you don't like it spinning then attach a brake to the prop shaft. Some transmissions will lock the shaft if you put it in reverse which is preferrable to spinning. Find out which transmission you have then look up the information about that transmission.

Good luck.

kind regards,
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Old 28-11-2013, 13:26   #3
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Re: Prop spinning under sail ???

Thanks for the question. I've been meaning to ask b/c I have exactly the same situation: 4108. 3-blade prop. Spins once we get up to about 4 knots. Transmission will not lock, no matter what position the gear shift is in (unlike other boats I've sailed).

Likely a silly question, but how do I know if I have a Velvet Drive? Is it indicated on the tranny somewhere? If it isn't a Velvet, why wouldn't it lock in place? And why is it bad to have it spinning?
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Old 28-11-2013, 13:44   #4
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Re: Prop spinning under sail ???

mine spozed to spin
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Old 28-11-2013, 13:53   #5
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Re: Prop spinning under sail ???

i've got a perkins 4-108 with a velvet drive transmission and 3 bladed prop.

according to the velvet drive manual it's ok for it to spin while under sail. but it is noisy and i've often thought about just clamping a vise grip around the shaft and letting it jam up against the hull. the reason i haven't done that is because i'm afraid i'll forget to remove it when i need to use the engine...

the reason you can't let some trannys spin under sail is that their internal oil pump doesn't function under those conditions and you would cause unnecessary wear on the gears.

mike, the velvet drive has an information plate on it but mine is so covered in paint i can't read it anymore.
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Old 28-11-2013, 15:29   #6
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Our Velvet drive is the same and all that I have read says that it is ok for them to spin and the only way to stop it is some kind of external brake. Being a hydraulic gearbox they decouple once the engine is off as there is no pump pressure.
There are also two schools of thought about the drag from the freewheeling prop and whether it is a problem or not. I didn't care about drag but I did not like the noise so I use a length of thin cord with a loop on the end which I snag on the coupling bolts once we are under way. Stops the freewheel noise and is light enough that should I forget it or need to start the engine in a hurry it will just snap off.

Matt
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Old 28-11-2013, 15:52   #7
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Re: Prop spinning under sail ???

Quote:
Originally Posted by onestepcsy37 View Post
mike, the velvet drive has an information plate on it but mine is so covered in paint i can't read it anymore.
Many thanks for the info. I've never seen a plate, but nor have I gone looking. Based on the searches I've been doing I believe mine is also a velvet drive. At least that's what it looks like it. But on the off chance it isn't a Velvet, what would cause an otherwise perfectly-working tranny to behave like this? Why wouldn't I be able to lock the tranny?

And I like your idea of a thin line as a stopper Matt. Like everyone else, the noise is annoying, but I don't really like the idea of a using a solid brake. Knowing me, I'd forget about it.
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Old 28-11-2013, 16:54   #8
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Re: Prop spinning under sail ???

Quote:
Originally Posted by GILow View Post
I didn't care about drag but I did not like the noise so I use a length of thin cord with a loop on the end which I snag on the coupling bolts once we are under way. Stops the freewheel noise and is light enough that should I forget it or need to start the engine in a hurry it will just snap off.

Matt
wow! great idea gilow! having a v-drive my coupling is very accessible under the compaionway stairs. going to have a look at it and see where i can do the same....
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Old 28-11-2013, 23:12   #9
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Quote:
Originally Posted by onestepcsy37 View Post
wow! great idea gilow! having a v-drive my coupling is very accessible under the compaionway stairs. going to have a look at it and see where i can do the same....
Lucky you. My access is hopeless but it still worth fiddling around for the subsequent lack of drive train noise.
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Old 28-11-2013, 23:47   #10
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Re: Prop spinning under sail ???

Quote:
Originally Posted by MapleSugarMan View Post
Anybody else out there own a 1980 Cal 39? We bought one about 18 months ago and we love it, but I'm perplexed.

I've always understood that when under sail it's best to put the engine in reverse to prevent the prop & shaft from spinning when the oil pump is not running to provide lubrication.

On our boat, which has a Perkins 4-108 engine with a 3-bladed prop, it doesn't matter whether we have the engine in neutral, forward or reverse, we can hear the prop spinning when we're under sail, even in relatively light wind.

Every instinct I have shouts "This can't be good!" But is it normal for one of these? If not, what do we do?

Does anyone have any thoughts or advice? You can answer here or e-mail me directly at BackYardMapleVT@Hotmail.com.

Thanks!
ours spins when the tranny oil gets a little low might be worth checking the level

Steve
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Old 29-11-2013, 02:42   #11
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If the school of thought that a locked shaft has no effect on drag, then I can'tsee why anyone would spend the money on folding or feathering props.

Be aware that the shaft is spinning in the reverse direction, which makes coming up with a brake idea a little easier in my mind.

Maybe fashion a small piece of wood to wedge against the hull with a shock cord to pull it clear once you start the engine and put it in forward.

A mechanic once told me to simply use a pipe wrench. It would loose it's bite once the engine started to turn in the opposite direction (forward ). If you could position that on the underside of the shaft, with room for it to fall clear, that would work. But you could follow that same rule of thought with the stick of wood wedged against a coupling bolt.
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Old 29-11-2013, 02:53   #12
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[QUOTE="Minggat;Be aware that the shaft is spinning in the reverse direction, .....


Are you sure about that?

Physics and hydrodynamics says otherwise...

Or do you sail in reverse?
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Old 29-11-2013, 03:02   #13
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Gaww !!

Recalling (or my failure to) what that mechanic said, I only scratched my head twice. I should have given it one more scratch.
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Old 29-11-2013, 05:05   #14
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Re: Prop spinning under sail ???

Quote:
Originally Posted by Minggat View Post
If the school of thought that a locked shaft has no effect on drag, then I can'tsee why anyone would spend the money on folding or feathering props.

Be aware that the shaft is spinning in the reverse direction, which makes coming up with a brake idea a little easier in my mind.

Maybe fashion a small piece of wood to wedge against the hull with a shock cord to pull it clear once you start the engine and put it in forward.

A mechanic once told me to simply use a pipe wrench. It would loose it's bite once the engine started to turn in the opposite direction (forward ). If you could position that on the underside of the shaft, with room for it to fall clear, that would work. But you could follow that same rule of thought with the stick of wood wedged against a coupling bolt.
A couple of points. The two schools of thought on freewheeling props are on whether there is more drag or less with the prop freewheeling. There is no debate that there is drag with both so the folding props still make sense for those who like them.

I also don't like the idea of anything that will score the driveshaft (think of replacing a pss seal, it would bugger the o rings if there was significant scoring) so I was not happy with the clamping wrench idea. Also, I could sort envisage the thing flying off and doing some damage. Unlikely I know but not out of the question.

Finally the stick idea is good but remember that if the boat slows the force on the prop may drop enough for the stick to fall out. Same goes for the looped line, it needs to be a pretty positive sort of engagement, you can't rely on constant force. Also, the stick needs to be light enough to yield without damaging anything if it is forgotten or if there is not enough time to remove it before engaging the prop.

Glad we sorted the rotation direction thing, it most certainly is not in reverse, not unless something has gone mighty wrong or you have a feathering prop. There is an old sort that will do this if you don't clamp them in the neutral position. I know as we had one that with a worn mechanism and you could watch the shaft spin forward for a bit, slow to a stop then eventually start to spin in reverse. Took a few minutes to proceed from one state to the other.

Matt
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Old 29-11-2013, 05:37   #15
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Re: Prop spinning under sail ???

If the trany is a Borg warner hydraulic there is no problem , the internal gears are moved with the engine runing and oil presure to, but wear in the stuffing box in the long run is another history, we solve this isue long time ago in our boat with a Max Prop....
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