OK, SO WHATS THE REAL ANSWER

[twodzusfittings]

I recently watched a You Tube Video from Lady K. It was in regards to: does one leave the transmission in gear or in neutral when under sail. I then searched the web and found reasons to and not to! Well, I'm confused. So I pulled up my PDF copy of the Universal M20 Users Manual and found this:
CAUTION: TRANSMISSION MUST BE LEFT IN NEUTRAL WHEN SAILING, DO NOT LEAVE IN FORWARD GEAR WHEN SAILING WITHOUT POWER AS IT WILL DAMAGE GEAR.

So what do you do? I'd appreciate all info on this matter.

 

[jssailem]

I put my transmission in reverse. It adds some drag (about .5 knots) but is better for me than burning up the transmission. Best recommendation is to follow the transmission recommendation.

Checking my Borg-Warner V-Drive manual I see this information.

The manufacture says it is ok. When surfing down the face of a wave at hull speed. I do not like the whine made by the speeding prop. Stopping the whine makes me feel better.

 

[Davidasailor26]

Best recommendation is to follow the transmission recommendation.

This. Yanmar / Kanzaki transmissions will have problems if left in reverse. Universal / Hurth are fine with reverse or neutral. Forward, as fast as I know, I’d never the right answer.

Alternatively, the real answer is to just get a folding or feathering prop.

 

[kloudie1]

I don't remember much guidance from the transmission folks until I saw the letter from Yanmar a few years back that advised sailing in neutral when the engine is off. I remember when I first started sailing about a thousand years ago that everyone sailed with the transmission in reverse. I have sailed my own boat many years with the transmission in reverse; I did have a difficult time once or twice getting it into neutral before starting the engine.. I was able to crank the engine in reverse on those occasions and then I could shift into neutral . I don't know what Yanmar was trying to protect against, but I suspect that some of the newer boats with switches to prevent starting while in gear may have contributed to their concerns. It also could be that the constant "jiggling" of the prop shaft from the propeller turbulence might brinell the bearings if left in the same location for a very long time (like days during a crossing without rotating the shaft?)
I dunno.. I sail in neutral mostly now but sometimes I go to my old habit to quieten things.

 

[jssailem]

Kloudie, I think it has to something to do with the transmission's ability to spread oil through the transmission to keep the gear box cool while free wheel spinning as you sail.

 

[Brian D]

Can't you inboard guys just take the motor out of the water, like us outboard guys? (snicker - snicker)

 

[Richard19068]

Transmissions and engines vary so only look at what people with your transmission suggest.

The best advice is usually what you read in your owners manual.

Everyting I've read about Hurth transmissions on M series Universal diesels says either neutral or reverse but never forward while sailing.

I usually leave mine in reverse while sailing because I don't want the shaft to spin. I don't care about the contraversy over this slowing me down by some fraction of a knot vs leaving it in neutral.

This is from a section on page 35 of the attached manual:

UNIVERSAL DIESEL WITH HURTH TRANSMISSION Model HBW-50 (2:1) Used on Models 12, M2-12, M-18, M3-20, M4-30, M25 and M-25XP Model HBW-100 (1.8:1) Used on Models 30, 35, and 40 Model HBW-150 (1.9:1) Used on Model 50 Model HBW-150 V-Drive (2.13:1) Used on All of our V-Drive Models CAUTION 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.

https://www.westerbeke.com/operator's%20manual/200157_m12-m50_operator_man.pdf

My understanding is what you don't want, among other things, is for the prop to turn the engine which could result in the engine's raw water pump filling up the system and flooding the engine cylinders because there is no exhaust pressure to blow the water out.

 

[Richard19068]

Can't you inboard guys just take the motor out of the water, like us outboard guys? (snicker - snicker)

Well I suppose we could but it just takes up too much room in the cockpit.

 

[danm1]

My understanding is what you don't want, among other things, is for the prop to turn the engine which could result in the engine's raw water pump filling up the system and flooding the engine cylinders because there is no exhaust pressure to blow the water out.

I've read this in connection with the forward facing direction of an external raw water strainer too, but I don't get it. Isn't the raw water cooling flow separate from the engine?

 

[Davidasailor26]

I've read this in connection with the forward facing direction of an external raw water strainer too, but I don't get it. Isn't the raw water cooling flow separate from the engine?

It is, but only until the exhaust, above the muffler. When water goes through the raw water circuit it dumps into there, usually in the exhaust line just after the manifold. If there is combustion that’s fine - the exhaust blows the water out. If there is no combustion the water backs up the exhaust into the cylinders.

I have not heard that the prop could spin the engine and fill the cylinders this way. I don’t think the torque from the prop could spin the engine. If it could all the people who sail in reverse could be turning their engines backwards. The bigger issue with sailing in forward is that some transmissions (Hurth in particular) are not designed to keep the propeller from spinning forward faster than the engine. When the prop is dragged that way it will slip the transmission and wear out the plates. Reverse on Hurth is OK because the reversing gear is designed to keep the prop from spinning forward ahead of the engine.

 

[Davidasailor26]

I have not heard that the prop could spin the engine and fill the cylinders this way. I don’t think the torque from the prop could spin the engine. If it could all the people who sail in reverse could be turning their engines backwards.

To correct myself slightly on this point, I just came across the following in the MaxProp instructions: “IMPORTANT: If the MAX PROP® is installed on a vessel that can attain sailing speeds over 15 knots, it is MANDATORY to return the transmission to neutral while sailing. If the transmission remains engaged and the propeller were to open (from hitting an object or water flow) it may turn the engine, flooding it, resulting damage to the engine.”

We generally don’t have boats that sail over 15 knots, so it’s probably a moot point, but it’s worth mentioning for completeness. The slipping plates are still the more traditional issue for sailing in forward.

 

[Tally Ho]

My O’Day 322 has a Yanmar engine and Kanzaki KM2P Transmission. I always sail tith transmission in neutral. I tried running it in reverse once. I had a hard time getting it out of reverse to start the engine after the sail.

If I really didn’t want the shaft/tranny spinning, I would figure out some sort of shaft brake.

Greg

 

[jssailem]

If I really didn’t want the shaft/tranny spinning, I would figure out some sort of shaft brake.

 

[Mandochamp]

Glad to see this thread and surprised at how many different answers there are. I had questioned this early on in becoming owner of a 1986 O'Day 28 with a 13.5 HP Westerbeke. I didn't like the idea of the prop spinning in neutral under sail; noise and that much more running of the shaft through the cutlass bearing didn't seem a great idea. I was told by an experienced guy to put it in reverse, so I had been doing that. I just finally looked hard enough to find out in my:
TECHNICAL MANUAL
WESTERBEKE
13 - 21 - 27 - 33 MARINE DIESEL ENGINES
In the manual page 108, point 4. I note I had to scan through 108 pages of the 117 page manual, but in the end, was glad to have the reassurance:

"4. OPERATION WITHOUT LOAD
Rotation of the propeller without load, e.g. while the boat is sailing, being towed, or anchored in a river, as well as idling of the engine with the propeller stopped, will have no detrimental effects on the gearbox.

Locking of the propeller shaft by an additional brake is not required, since locking is possible by engaging the reverse gear. Do not sail while engaged in forward."

 

[Clutch Cargo]

I cut my teeth in the small boat business working at a marine transmission company back in the day. So, at the risk of sounding condescending, the real answer is to do what the manufacturer says in a published manual for the specific gear that you are using. Not what someone told you at the marina, yacht club, diesel shop etc. and certainly not what you would like or prefer. The manufacturer has a vested interest in making sure the product works as promised and survives through its normal service life; and as someone who works for a manufacturer, noone on "our side of the wall" likes seeing chronic failures or unhappy customers.