transmission position while sailing

[Alice A.]

There are apparently conflicting opinions about whether to lock the transmission in reverse while sailing or to leave it in neutral. We have a 3HM Yanmar in a Hunter 37.5., with a Martec folding prop. We were always told to shift it into reverse while sailing because it's not good for the transmission to let the prop freewheel. Recently a friend spoke to someone from Yanmar who told him it sholud not be put into reverse. Does anyone know the correct information on this? Thanks, Alice

 

[Don S/V ILLusion]

One of the advantages of a folding or feathering prop is that it folds or feathers which obviates the need to be concerned with what to do with the transmission while sailing. Your shaft should not turn unless there is something wrong with the prop which prevents it from folding.

 

[Alice A.]

Would it do any harm to put it in reverse or should it always be left in neutral? My friend has a Flexofold that won't fold unless the transmission is put in reverse.

 

[Ed Schenck]

Not quite Don. With my Flex-O-Fold the shaft will turn if left in neutral or forward. On the recent midnight passages it was quite noticeable, only the sound of the water and the tranny until I remembered to move it to reverse.

 

[jdhohmann]

We also have that problem sometimes, when we are under sail, our prop doesn't always fold down as it should, resulting in the shaft turning. So I put in into either forward or reverse, then put it back to neutral. This help the prop fold and everything is great after that!!!!

 

[Grizz]

Oh no! Not again...

...thought this was killed and relegated to the archives w/ the rest of the reference material on this topic. Guess 'Groundhog Day' wasn't too far off...

That beeping sound you hear is my transmission placed in reverse while under sail, allowing the Martec to fold and create the illusion of at least an increase of .03 knots of boat speed. Maybe...

 

[Guest]

Tranny

At some risk of being relegated to forum purgatory for the umpteenth time, our boat has a Yanmar 4jh engine with a KBW 20 transmission driving a fixed three blade prop. According to the Yanmar Service technician that I talked to some time ago he told me that unless we were crossing oceans leaving the transmission in neutral for extended periods while under sail would do no harm. So that is what I do. The prop does spin at a slow rate, which does to some degree reduce drag to a greater degree than leaving the transmission in gear.

As with other much covered topics of this type opinions run amuck. If you want to peer into the archives for the umpteen opinions about sailing with the transmission in or out of gear, I welcome your trepidation spirit. You might even find another's opinion worthy of a solution for your situation.

Terry Cox

 

[Alice A.]

Re: Tranny

I was not aware that some people who read the forum are weary of this topic. I guess I haven't been reading it as long as some others. And, by the way, I have found it much more difficult to look back at the archives since the website changed. I will try again. Alice

 

[Guest]

Tranny

Hi Alice, if I left you with the feeling that this is a topic that some have become weary over, please accept my apologies. All questions, regardless of how often they are posed, simple or complex, need to be answered with aplomb. I've been contributing to this forum for a number of years and I can assure you this topic has been covered many times and I have given the same basic reply, in hopes that I can be of modest help to those who are merely looking for some advice, even if it is for the umpteenth time. Once upon a time I was an ill informed, inexperienced sail boat owner just looking for some answers like many who visit this site. Now I am just a sail boat owner.

Terry Cox

 

[Scott B]

Alice, this question comes up from time to time along with waxing and brewing coffee, .... everyone has an opinion and can lead to some passionate discussions. But, I find the search difficult to find some answers as well.
This is a recent discussion on Freewheeling vs, Locked Prop

I would encourage others to refrain from scarcastic repsonses to questions being asked for the umpteenth time, if someone has searched, not found an answer... where do they turn ??? The whole idea of the forum is to ask, discuss and find answers right ??


BTW, I did read either in the Yanmar manual, or online at Yanmar or Kanzaki to put it in reverse.

 

[PHitchcox]

A good reason for this site - to let out a few questions, maybe asked before, maybe needing to be asked again.

One element of the answer to point at - does it do the tranny damage? Most likely not much, given our usual use of our boats. Does it produce drag? Apparently a little. So using reverse should be okay. Leaving it in neutral won't do any harm either.

Here's a new point I came across recently - even with a folding prop, I was advised to still orient the shaft with the blades horizontal and lined up with the keel. Now that's getting every last fraction of a knot....and is one reason why this question can be asked again. Thanks Alice.

 

[Ray T]

Alice, A Martec should be aligned vertically. If you don't do this one blade will hang down creating drag. If you are interested in the least amount of drag line up the prop vertically and mark the shaft and the transmission housing. If the prop is folding properly It doesn't make any difference if you leave the transmission in forward, reverse or neutral the shaft will not rotate. When I was racing my Cal I left mine in neutral, never had the shaft move.

 

[Benny]

It is not that important. Follow your manufacturers recommendations. Yanmar indicates that it is acceptable to freewheel the prop as the transmission is a wet sump and will be lubricated at all times. They also agree that if you want to lock the prop with the transmission you should do it on reverse. Some claim that a freewheeling prop will cause undue wear on the gears and bearings by turning, while others point out the undue stress forces caused by unleveled forces cause by a shaft trying to turn. The reality has been that under either practice the transmissions have proved to provide outstanding reliability. With wear factors being apparently inconsequential it is my preference to freewheel as 1) a freewheeling prop offers less drag and 2) I do not have to slow the boat down or stress the clutches to shift back into neutral or start the engine in reverse like some do. You have a folding prop which should render this discussion mute as when the shaft has no engine driven rotation the blades should fold and negate a drag induced rotation. The propeller is always facing in the same direction and when the boat is moving forward the force will always be in the rotation direction which for most Yanmars is RH. The answer to your question is that you are in a class least to worry about an insignificant question.

 

[Alice A.]

Thanks to all of you gentlemen who replied to my question. We have been sailing our 37.5 for 14 seasons with the Martec set in reverse, with no apparent ill effects. We are former very serious racers who are performance oriented. On our race boats, we always lined up the shaft to get every tenth of a knot. We race our Hunter occasionally with usually good results. I raised the question only because a friend was recently told by someone from Yanmar not to leave the transmission in reverse while sailing. I have noticed that sometimes it is difficult to shift from reverse to neutral when starting up after sailing. Perhaps that is why there could be a caution. Thanks again, Alice

 

[Guest]

Tranny

You are welcome Alice.

Terry Cox

 

[Benny]

We are glad to be of help but perhaps would be of more help if you would state your doubts or questions straight up.

 

[Al - s/v Persephone]

Alice -

A number of years ago I saw a reference to a US Navy study (David Taylor Model Basin, if I recall correctly) that found that a fiixed 2-blade prop had less drag than a free-wheeling one, but that a 3-blade prop had less drag when free-wheeling.

In the thread referenced above I posted the following results of actual controlled experiments with 2 Hunters I owned - one with a 2-blade and one with a 3-blade - that seem to support the Navy results:


Some experimental results

At the risk of not fitting-in with the theorizing about the subject, I can offer two real data points from personal controlled experiments.

While the spring and fall offer good winds between Capes Ann and Elizabeth, we have frequent light airs during summer. The subject of getting the most speed out of them has been a bit of an obsession with me, and the prop drag minimization question led me to do some experimenting.

My last boat had a 2-blade prop and, asI had been told it would, exhibited the least speed reduction when fixed.

With no other changes to sails, course, etc., when doing 4 or 5kts in flat water, fixing the transmission in reverse consistently gained me 0.25kt which I lost when going back to free-wheeling.

(Each time I tried this, I repeated the changes several times, with 5min in each state, which allowed the speed to stabilize.)

That boat, and my present boat, are similar hull-forms (1999 Hunter 310 and 2005 Hunter 36). I was very surprised, therefore, to find that my present boat's 3-blade cost me 0.5kt in the same conditions when I fixed it, but the reduction was quickly gained back when I free-wheeled.

Since I had taken the precaution of verifying that the cone-clutch transmissions on my Yanmars in both boats could free-wheel without lubrication issues, I have put over 6,000nm of shaft-spinning on my transmission with no apparent ill effects on it or my cutless bearing.

When I'm squeezing 3.5-4kts out of 5kts of true wind it makes a big difference. The extra 0.5kt has often made it possible to get somewhere sailing without overly trying my wife's patience, when others were motoring.

Fair winds,
Al
s/v Persephone

 

[dilligaf]

I own a Hunter 326 we leave the transmission in Neutral, The Jeanneau DS49 has a max-prop, I leave the transmission in Reverse, to fold the prop and find .8kt improvement...
Dilligaf

 

[MsEmee]

BTW, I did read either in the Yanmar manual, or online at Yanmar or Kanzaki to put it in reverse.

Scott I don' t know where you are getting the reference on the Kanzaki transmission to put it in reverse. My manual has a big Warning not to do to this at all for this will cause damage to the transmission. When I sent my transmission back to Mastry Engines for a new thrust bearing they asked if the transmission was ever locked in reverse. I told them I didn't know what the previous owner did, as this was a new to me boat at the time. Total engine hours 110. They also said to leave it in neutral. The Kanzaki transmission doesn't have a pump in it. The gear oil just lies in the bottom of the case where the gears pick up the oil and sling it around. Putting the transmission in reverse puts undo stress on the gears and shifter lever horse colllar that are not made for to this. Mastry Engines had to replace these parts because of wear.
Melissa
2006 Hunter 36, 3YM30 engine.