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Hi

Have a 2009 Beneteau 40 with Yanmar 4JH4AE engine. Sorry ... don't know which transmission.

Was told when bought boat in 2011 not to put it in reverse when sailing (to stop prop turning). If I put in reverse then have to almost stop boat to get into neutral.

I have now read that leaving shaft turning while sailing leads to much quicker wear so should engage reverse.

Any comment?

I will try and find transmission type but info plate on engine leaves this space empty!!

Thanks, JohnB40
 

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John,

It depends on the transmission. Some need it locked some can handle free spinning. Either way it is faster to keep the prop from spinning so neutral is generally the worst option unless your folding/feathering prop prefers it.
 

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. Either way it is faster to keep the prop from spinning so neutral is generally the worst option unless your folding/feathering prop prefers it.
Completely untrue.... Old wives tales die hard...

Yanmar adamantly and strongly advises their gears be locked only with a shaft brake or allowed to free spin...
 

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Kynntana (Freedom 38)
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The spinning prop will drive you crazy. I put it in reverse while sailing, then put the boat in irons to slow it down and get it into to neutral before I crank the engine. It slides right in if there's no pressure. I think the problem comes when trying to force it out of gear. I have a Yanmar 3GM30. Anyway, as you'll see,the advice on this seems to be all over board....
 

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The spinning prop will drive you crazy. I put it in reverse while sailing, then put the boat in irons to slow it down and get it into to neutral before I crank the engine. It slides right in if there's no pressure. I think the problem comes when trying to force it out of gear. I have a Yanmar 3GM30. Anyway, as you'll see,the advice on this seems to be all over board....
The problem comes because water movement over the prop wears the cones over time and eventually causes slipping of the gear necessitating a rebuild. Yanmar had so many issues they issues an MSA on the topic to all dealers. Folks have also broken gear linkages etc..

Yanmar MSA - Gear Position While Sailing


Advisory Number: MSA08-003:

DATE February 8, 2008 Dealers and OEMs
TO: All Marine Distributors
SUBJECT: Gear in Neutral While Sailing All MODELS:

All Sailboat Engines

We continue to get questions regarding the correct gear position while sailing with the engine OFF. This advisory is issued as a reminder; Yanmar requires that if sailing with the engine OFF (not running) the transmission shifter must be in the neutral position or internal damage to the gear or sail-drive will result. This damage will not be covered by Yanmar’s Limited Warranty. Please instruct customers and dealers who deliver the sailboat to the customer, of the correct (Neutral) position for the marine gear while sailing.

If the customer desires that the propeller shaft not spin while sailing, either a folding propeller, shaft break, or other suitable device may be used. However, Yanmar accepts no responsibility for the selection, installation, or operation of such devices. Please also refer to Marine service advisory “MSA07-001_Yanmar Sail Drive Propeller Selection” for additional information.

If you have any questions regarding this advisory please contact a Customer Support representative.
 

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As I said it depends on your transmission. But allowing the prop to spin, ie neutral without a shaft break, is slow.
 

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This is incorrect. Their is no reason a spinning prop would create more drag than a fixed one (except folding props of course). The opposite is almost certainly true.

Sent from my XT1060 using Tapatalk
 

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Kynntana (Freedom 38)
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See study results (link below) from 2008, which stated the following in its findings, though I still contend that a rotating propeller will Drive_You_Crazy: "The experimental results confirm that a locked propeller produces greater drag than does a freewheeling screw (up to 100% more drag was observed, this being at higher speeds). Furthermore, for the freewheeling case, the magnitude of the hydrodynamic resistance is significantly affected by the amount of frictional torque on the shaft, low torque being accompanied by low drag."

Sailboat propeller drag
 

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Note that Yanmar does allow you to shift into reverse while sailing if you have a folding or feathering prop. That's good since some props won't fold or feather without locking the shaft. Even so I usually put it into reverse for a few seconds, then back into neutral when the prop feathers.

When I had a non-feathering prop I did confirm on my own boat that freewheeling was faster than locking the prop shaft.

Putting on a feathering prop last winter was the best performance upgrade that I've made to the boat.
 

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So let me get this right. It's ok to either leave it in reverse or pop it into reverse briefly to get it to stop spinning given I have a max prop ?
 

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So let me get this right. It's ok to either leave it in reverse or pop it into reverse briefly to get it to stop spinning given I have a max prop ?
I would pop it into reverse to get it to feather, then go back into neutral just in case some weeds force it to un-feather...
 

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Kynntana (Freedom 38)
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As I said it depends on your transmission. But allowing the prop to spin, ie neutral without a shaft break, is slow.
This is incorrect. Their is no reason a spinning prop would create more drag than a fixed one (except folding props of course). The opposite is almost certainly true.
Sorry you have it backwards. A freewheeling sailboat prop has LESS DRAG not more..
This is what gets me about sailing. It is extremely difficult to sort out which variables apply to one thing and not another. Even though I posted that paper that said a spinning prop is faster on hull speed than a locked prop, I asked a couple of very experienced sailors, one of which is a pilot who said that if you need to glide to a landing without stalling your forward momentum, then you lock the prop and that keeps the plane from slowing down. He wondered if the paper was related to large vessels and not smaller sailing yachts. These two said they both lock their props; however, they also have folding ones....so maybe there's a difference with a 2-blade fixed prop? Feathering props?
 

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This is what gets me about sailing. It is extremely difficult to sort out which variables apply to one thing and not another. Even though I posted that paper that said a spinning prop is faster on hull speed than a locked prop, I asked a couple of very experienced sailors, one of which is a pilot who said that if you need to glide to a landing without stalling your forward momentum, then you lock the prop and that keeps the plane from slowing down. He wondered if the paper was related to large vessels and not smaller sailing yachts. These two said they both lock their props; however, they also have folding ones....so maybe there's a difference with a 2-blade fixed prop? Feathering props?
We are NOT in planes or helicopters and not traveling at those speeds in that medium. The University of Strathclyde Ocean Engineering Department paper was specific to sailboat props as was the MIT Sailboat Prop study. MIT also found the SAME THING. I also tested this years back and still have the test jig for conducting the analysis. I put a video up on YouTube...

*Why will a folding prop remain open and spinning when under sail and the gear placed in neutral?

*why does the same prop slam shut the split second it is locked in reverse?

*why does my dingy motor leg stay down when being towed in neutral but the minute I lock it in reverse the prop lifts/tilts the motor...?


Beyond MIT & The University of Strathclyde Dave Gerr author of the Propeller Handbook says the same and the UK magazine Yachting Monthly also tested this specific to sailboat props... Lots of "experts" have been wrong on this for many years.
 

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I used to slip my boat into gear to stop the annoying whirring noise, but only for a few months of ownership, then I installed a Flexofold over the winter.

Many years ago I worked for a company that flew us daily to the job site in a twin engine Piper Navajo. That was until we blew the right engine, complete with a brief fire over Southern Ontario. What are the first things a pilot is taught to do? Feather the prop and cut the fuel. If the prop is not feathered there is sufficient drag to make the plane very difficult to fly. As it was I got a great view out of the side window of the runway from my left seat as the plane crabbed it's way down final on the power of the left engine only.

Just imagine taking an 18" fixed blade prop and trying to hold it down in a 5 or 6 knot current, first spinning, then locked. Maine Sails example of the engine on the tender is a great one! It would be easy for anyone to replicate, if you are willing to trust someone else at the helm while you are hanging out in the tender.
 

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Kynntana (Freedom 38)
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I went out in my 2-blade fixed sailboat about a week ago to meet friends across the bay so no rush to get anywhere. I had consistent 15-knots on a port tack so I would head into the wind periodically, shift into reverse or neutral, and see what that did to my SOG when the sails powered back up. Did it a few times. It was pretty consistent with 7.3 to 7.4 knots on the fixed prop and 7.6 to 7.7 on the spinning prop.
 

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This is incorrect. Their is no reason a spinning prop would create more drag than a fixed one (except folding props of course). The opposite is almost certainly true.

Sent from my XT1060 using Tapatalk
Correct. The latest info is: a spinning prop has aprox 300% less drag than a fixed prop. A spinning prop mean faster sailing.
 

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Correct. The latest info is: a spinning prop has aprox 300% less drag than a fixed prop. A spinning prop mean faster sailing.
I think that may be a typo. Can you provide a source. The numbers that I have seen vary between 2-3% up to closer to 10% increase in drag for a locked prop. But even that range is also very dependent on the prop installation and specific propeller.

For example, locking a two blade prop vertically in a an aperture greatly reduces drag. Or 'power' props tend to throw off large amounts of tip vortex turbulence when spinning. Dragging that ball of turbulence through the water can actually increase drag over a locked prop.

Jeff
 
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