Drive shaft spinning under sail

[Far Out]

Hi all,

I was sailing along yesterday when I heard a rythmic "thup-thup-thup" sound coming from under the cockpit sole. Thinking that my transmission was out of gear, I checked the transmission handle and found that it was in forward. I moved the handle to reverse and the noise stopped. Only now the handle would not go into neutral or forward gear.

Thinking that this was not right, I checked below. I found and touched the transmission lever, and suddenly the handle would go between forward and reverse. But I could see that the shaft was spinning when I was in forward gear and neutral, but not when I was in reverse. Under power the drive shaft behaved as I expected, and I didn't have any problems when I was motoring back to my slip.

I have a 16-hp Yanmar diesel that I think is original, and I assume that it has the transmission that came with the boat.

Can anyone explain what I was seeing, what I did wrong to make it start happening, and how much it's going to cost me to fix it?

Thanks for your help,
Chuck

 

[Christian Williams]

Not sure anything's wrong. The usual practice is to put the transmission in reverse to keep the prop from spinning while sailing. Or you can put a pipe wrench on the shaft every time. Or install a shaft brake.

Stand by for heavy forum weather (not here, but everywhere else the argument rages).

Yes, a stopped propeller does slow a boat down, and yes, a boat goes faster with a freewheeling prop. But the noise drives any sane person nuts.

A prop may spin when the transmission is in forward gear. In fact, putting the trans in forward gear was recommended in many Ericson owner manuals.

However, or meanwhile, it is widely contended that a transmission left in forward while sailing damages the transmission.

Generally these warnings and counter warnings are in red letters and upper case.

If your transmission works fine, just put it in reverse gear while sailing. Anyhow, that's what I do.

Only now the handle would not go into neutral or forward gear.

Most Ericsons could use new Teleflex (Morse) control cables. Not expensive, and makes shifting smooth as butter.

 

[Alan Gomes]

Hi all,

I was sailing along yesterday when I heard a rythmic "thup-thup-thup" sound coming from under the cockpit sole. Thinking that my transmission was out of gear, I checked the transmission handle and found that it was in forward. I moved the handle to reverse and the noise stopped. Only now the handle would not go into neutral or forward gear.

Thinking that this was not right, I checked below. I found and touched the transmission lever, and suddenly the handle would go between forward and reverse. But I could see that the shaft was spinning when I was in forward gear and neutral, but not when I was in reverse. Under power the drive shaft behaved as I expected, and I didn't have any problems when I was motoring back to my slip.

I have a 16-hp Yanmar diesel that I think is original, and I assume that it has the transmission that came with the boat.

Can anyone explain what I was seeing, what I did wrong to make it start happening, and how much it's going to cost me to fix it?

Thanks for your help,
Chuck

Hello, Chuck.

There is a great deal of information on the subject of whether you should leave your transmission in neutral to freewheel or keep it in gear (either forward or reverse). Take a look at the archives at the Sailboat Owner's site, for example.

The bottom line is that it depends on the particular transmission in question. For a Yanmar with a Kanzaki transmission you should leave it in neutral. It is possible to damage the transmission otherwise. In fact, Yanmar will void your warranty for not following this procedure. Obviously, your engine is long out of warranty, but I point that out just to give you Yanmar's view of the matter.

I realize that this does not answer directly the question you are asking, but as a practical matter you should leave it in neutral. If you find the rotation of the shaft excessively disagreeable then the solution would be to install a shaft brake and not rely upon the transmission gears to keep the prop from rotating.

Cheers,
Alan

 

[Christian Williams]

not rely upon the transmission gears to keep the prop from rotating.

Citation, please.

 

[Alan Gomes]

not rely upon the transmission gears to keep the prop from rotating.

Citation, please.

Yanmar Technical Bulletin dated 11.18.11:

View attachment YMTQTB11-017 (1).pdf

 

[Loren Beach]

As pointed out, the Yanmar instruction for transmission shift position under sail is probably different from the (more common engine in Ericson's) Universal instruction to lock it in reverse to stop it from spinning. I have read this in my engine manual.

 

[Alan Gomes]

As pointed out, the Yanmar instruction for transmission shift position under sail is probably different from the (more common engine in Ericson's) Universal instruction to lock it in reverse to stop it from spinning. I have read this in my engine manual.

Indeed. For that matter, not all Yanmars are fitted with Kanzaki gear boxes. Some have transmissions manufactured by Hurth. The bottom line is that one's course of action here is transmission-specific.

Since the original question had to do with a 16 hp Yanmar, I'm going on the assumption that it is a Kanzaki box with a cone clutch (likely a KM2P?). It would be important for Chuck to confirm all of this to leave no doubt.

 

[SailorDrew]

1978 E-27, wheel steering, Yanmar YSM-8--which original transmission?

I too, wonder about wether to leave the engine in gear or not when sailing and hear conflicting advice. So, it depends on the transmission then. . Does anyone know what transmission was used in the 1978 E-27 with the Yanmar YSM-8 with wheel steering, one of the last ones built? If it's the Kanzaki, leave it in reverse, then?

 

[Alan Gomes]

I too, wonder about wether to leave the engine in gear or not when sailing and hear conflicting advice. So, it depends on the transmission then. . Does anyone know what transmission was used in the 1978 E-27 with the Yanmar YSM-8 with wheel steering, one of the last ones built? If it's the Kanzaki, leave it in reverse, then?

If it is a Kanzaki with a cone clutch then that would be neutral, not reverse. But you'll need to do a bit of checking to find out what transmission it is.

 

[Far Out]

Thanks for the advice everyone. I'll check my transmission and see what I've got.

 

[JPS27]

where does one find shaft brakes for our smaller sized Ericsons? I've never heard of this option. I have used reverse to stop the spinning prop.

I have a kanzaki on my ancient yanmar 2qm15. I also have about 2 inches of exposed shaft left to work with between the stuffing box and the shaft coupling.

 

[Alan Gomes]

where does one find shaft brakes for our smaller sized Ericsons? I've never heard of this option. I have used reverse to stop the spinning prop.

I have a kanzaki on my ancient yanmar 2qm15. I also have about 2 inches of exposed shaft left to work with between the stuffing box and the shaft coupling.

Though someone else may have an answer to your question, I guess I'd first ask about the noise level with it spinning. This seems to vary a great deal from installation to installation. On my little E26-2 I don't hear a thing. On a previous boat I could not hear anything, either. But others--including Chuck, who started this thread--do, and may find it objectionable.

The only reason I ask is that, apart from noise, there is no reason to lock the prop for these transmissions. It will not make the boat sail faster. In fact, MaineSail's tests show that a freewheeling fixed prop provides somewhat less drag under sail than a stationary one. So if the noise isn't bothering you then just shift into neutral and enjoy!

 

[Christian Williams]

As I said, all these issues have conflicting recommendations.

In general, a free-spinning prop raises questions of transmission wear.

At random: http://www.endeavourowners.com/dscsn/systems/propulsion/frewhl.html

Matter of who you believe. Here is Nigel Calder, in "Boatowner's Mechanical and Electrical Manual," Third Edition, 2005.

He says that a freewheeling propeller is OK for a manual transmission, "except that it creates unnecessary wear on bearings, oil seals, and the shaft seal," and that it makes "quite a racket."

He suggests locking the shaft "simply by putting the transmission in gear...Note that you must always lock the transmission in the opposite direction to that in which the boat is moving (i.e. in reverse). If you don't, the clutch may slip and burn up (the critical speed at which this happens on Hurth transmissions seems to be around 6 knots)."

 

[woolamaloo]

I referred to Page 35 of the Universal Marine Diesel Owner's Manual which covers my M-18 with a Hurth transmission as well as the M-25 and M-25XP some of you others have. The manual cautions: "Do not leave gear in forward when sailing. Gear must be in neutral for free wheeling or shifted into reverse to lock propeller while sailing." That's not exactly decisive as to which is better.

On page 10 of the same manual, Step 2 under "Stopping the Engine" instructs: "Place transmission shift lever in neutral. (Center Position). Step 3 - Leave engine idle for approximately 1 to 2 minutes for it to cool down."

What that has mostly led to is that by the time I actually stop the engine, I'm no longer thinking about the prop and I leave it in neutral by default. My forgetfulness often decides for me. Luckily, that's one of the okay positions. If I think about it, I'll put the transmission in reverse if I'm really moving. But if boat speed is at a premium and the thought of that additional resistance is painful to me, I'll leave it in neutral. I wish there were a definitive answer.

I have never noticed the sound of the prop moving when I've left it in neutral. I get no "thumping" even when I've seen it spinning.

 

[Christian Williams]

Personally, if it weren't for the noise I'd let it spin, especially in light air when my 3-bladed fixed prop really slows the boat down.

But on the E38, a freewheeling prop sounds like the engine is running.

Offshore, when charging the engine in neutral and surfing at 8 knots, the noise is so loud I have to shift to forward gear to keep it from overspeeding.

Another reason for a folding or feathering prop?