Why does Yanmar recommend leaving SD20 in neutral while sailing

[MikeTC]

I have been leaving SD20 drives in gear (fixed props) and wonder if this has caused two prop shaft seal failures in 18 months. Two Yamar dealers said it should be OK to leave in gear while sailing.

[Dulcesuenos]

In neutral it spins sometimes faster then your motor would ever turn it, so definitely more wear and tear and heat etc. we only motor at 6 to 6.5 but can sail 9+, we always locked ours in reverse. Now we have folding props so problem solved.

[Tornadosailing]

There shouldn't be any problem leaving them in gear, except for the very high drag created by the props. Folding or feathering props for sure.

[StuM]

This comes up quite often.

a. Leaving them in gear with a fixed prop will increase drag considerably.
b. Yanmar put out an advisory for a reason.

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.

[StuM]

Further data:
http://www.endeavourowners.com/dscsn...TQTB11-017.pdf

[Tornadosailing]

Originally Posted by StuM

Further data:
http://www.endeavourowners.com/dscsn...TQTB11-017.pdf

Good info, but doesn't work on my boat. I have one of only a couple boats with my particular configuration. A Salina 48 with Brunton Autoprops will instantly round up if the saildrives are ever placed in neutral. Weird, strange, and makes no sense, but true. Took me 6 hours to figure out how to make the boat sail with motors off. It will even round up with only the headsail, no main. Another CF member has the same boat/prop combo and had been fighting the problem for 2 years. My solution of simply shutting off the motors in forward gear worked for him as well.

[Dulcesuenos]

Originally Posted by StuM

Further data:
http://www.endeavourowners.com/dscsn...TQTB11-017.pdf

Sd 20 doesn't have a cone clutch not sure what slippage or damage could ever occur

[malbert73]

Originally Posted by Tornadosailing

Good info, but doesn't work on my boat. I have one of only a couple boats with my particular configuration. A Salina 48 with Brunton Autoprops will instantly round up if the saildrives are ever placed in neutral. Weird, strange, and makes no sense, but true. Took me 6 hours to figure out how to make the boat sail with motors off. It will even round up with only the headsail, no main. Another CF member has the same boat/prop combo and had been fighting the problem for 2 years. My solution of simply shutting off the motors in forward gear worked for him as well.

6 hours to learn to sail boat with motors off? Is that even a sailboat? Yikes.

[Tornadosailing]

Originally Posted by malbert73

6 hours to learn to sail boat with motors off? Is that even a sailboat? Yikes.

I was so mad I was ready to burn it to the waterline.

The rudders are behind the props, and very close to them. When you put the motors in neutral the Autoprop blades flip somewhere between the feathered position and reverse position, then freewheel backward. This creates a large disturbance ahead of the rudders and destroys the waterflow across them. The boat is uncontrollable and rounds up immediately. It took this long to figure out because it would happen even if you were only running the headsail, which still makes no sense to me. And it happened so fast you had no time to experiment with anything. It was an immediate fight for control.

As far as I know, the FP Salina is the only boat that has this problem with the Autoprop.

[wiekeith]

Originally Posted by StuM

Further data:
http://www.endeavourowners.com/dscsn...TQTB11-017.pdf

Ah, that's exactly what I do with my SD50 fitted with a folding prop - put it into reverse momentarily then back to neutral. Reassuring to know it's the recommended method. :-)

[Capt. Ray]

Over the past few years there have been multiple experiments done by well-regarded publications that have generated conflicting reports about which presents the highest drag - freewheeling or locked propellers; the latest wisdom seems to be that freewheeling is least drag! Go figure. But either way I would not call it "very high drag" except when you're concerned about a tenth of a knot here or there while racing...

So to saildrives (I hate those things!) - I have sailed a catamaran with two Yanmar SD30s with folding props and I now also hate folding props - they never seemed to work right, even at 10 knots they only randomly folded, and many, many a day over 8,000nm I was forced to lock the drives in reverse or have to put up with the constant noise from a spinning transmission when trying to sleep. And yes, the idea of constantly spinning the things, especially at catamaran speeds downwind, is a horrific concept since they are so susceptible to wear and tear not just seals but also cone clutches.

In one year I had to take both saildrives out TWICE to re-seal, obviously the first time was a botched job but those things do not fill me with confidence.

Ray

Originally Posted by Tornadosailing

There shouldn't be any problem leaving them in gear, except for the very high drag created by the props. Folding or feathering props for sure.

[contrail]

Originally Posted by Capt. Ray

Over the past few years there have been multiple experiments done by well-regarded publications that have generated conflicting reports about which presents the highest drag - freewheeling or locked propellers; the latest wisdom seems to be that freewheeling is least drag! Go figure. But either way I would not call it "very high drag" except when you're concerned about a tenth of a knot here or there while racing...

So to saildrives (I hate those things!) - I have sailed a catamaran with two Yanmar SD30s with folding props and I now also hate folding props - they never seemed to work right, even at 10 knots they only randomly folded, and many, many a day over 8,000nm I was forced to lock the drives in reverse or have to put up with the constant noise from a spinning transmission when trying to sleep. And yes, the idea of constantly spinning the things, especially at catamaran speeds downwind, is a horrific concept since they are so susceptible to wear and tear not just seals but also cone clutches.

In one year I had to take both saildrives out TWICE to re-seal, obviously the first time was a botched job but those things do not fill me with confidence.

Ray

I love my folding props. Yes, when the engine is stopped in neutral, they can keep spinning, which keeps the blades unfolded which keeps them spinning, etc. My technique is to stop them whilst sailing slowly (probably just the main), and momentarily put them in reverse. This stops the prop and they then fold and stay folded when I put them back into neutral. Works, every time.

[Capt. Ray]

This advisory makes some sense but I fail to understand what damage can come to a saildrive when locked in reverse while sailing. Sounds like weak design to me. A shaft brake (not "break"!) is a good idea but a pain in the arse to implement especially with a catamaran, requiring an interlock to make sure the shafts are not locked before running the engine. Interlocks, like any other equipment, can fail and just more complexity. The drive should be designed to handle it.

Now I think about it, every transmission should be designed with an infallible interlocked shaft brake system, maybe a cog or clutch that engages when in neutral?

Originally Posted by StuM

This comes up quite often.

a. Leaving them in gear with a fixed prop will increase drag considerably.
b. Yanmar put out an advisory for a reason.

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.

[a64pilot]

Originally Posted by Capt. Ray

Now I think about it, every transmission should be designed with an infallible interlocked shaft brake system, maybe a cog or clutch that engages when in neutral?

How about a “P” position

[shawndear]

For the last 7 years I have always put my engines into reverse whilst sailing as I cannot believe that a fast spinning prop is good for anything. In addition, the vibration from an undriven prop seems far worse than from a driven prop, and that can't be good for anything either. I also don't understand why the gears should not disengage after free wheeling as it spinning under engine power should be no different, so if there is an issue with it spinning after long periods of time of it getting stuck in gear, then should there not be the same issue with it in gear under engine power. I am suspicious of Yanmar, and wonder if they like it spinning so there is more wear and tear and therefore more clutch replacements and seal replacements. In addition, whilst the engine is running there is cooling water flowing through the saildrive to cool it. When freewheeling the prop will still spin but now there is no cooling water. What happens to all the heat build up through friction from it spinning, without water being pumped through to cool it? I have an sd30 on one engine and sd50 on the other. I still have the original cone clutch on the sd50 and have never replaced or cleaned it. I run this cat as a charter yacht and so use it 10 out of 12 months a year - relatively heavy use although I sail everywhere (with the engines in gear). It works for me, maybe not someone else! I have to admit my sd50 does not engage without high revs on occasion but not surprising when the cone has not been deglazed ever.