Why does Yanmar recommend leaving SD20 in neutral while sailing

[philiosophy]

Ok very good to know. Bought my boat with 450 hours on the engine and have a Gori prop. Up until recently it hasn’t been a problem because the Gori just folded and didn’t spin. Last crossing from Fiji to Whangarei NZ it wouldn’t stop spinning without putting it in reverse. So for agood 700 miles that how I sailed the boat thinking maybe it was damaging the gearbox to spin without the engine on. So have I damaged the gearbox and if so what damage occures by having it in reverse. I will try putting it in reverse then neutral.

[sailcrazy]

We have a Autoprop on our monohull, with the KBW20 transmission. The autoprop is supossed to feather and stop-but it never has! The only way I can keep the driveshaft from spinning is to leave it in gear (Fwd or Rvs). Once I put it back in Neutral, the shaft slowly begins to spin, and stays spinning-without any eng-driven lub taking place, only splash lub from the rotation (I'm guessing). Is it really better to leave it in Neutral, and spinning, when the eng is off?

[Kita]

Originally Posted by 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.

My thoughts are it's probably not getting lubricant very well when just prop shaft is spinning alone..when everything is spinning inside being driven by the engine the gear oil is splashing everything. .when just the shaft is spinning in neutral it's just not the same, much like the same reason you shouldn't tow an automatic car very far or fast for that same reason. .. the tail shaft bushing in the transmission does not get lubricated properly. But all this discussion sure makes me appreciate my Gemini catamaran. I just raise the outDrive up out of the water.....lol

[MikeTC]

Thanks for the Replies

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.


I would still like to know what damage is caused to the gears. I can only guess it lack of oil while there is a inconsistent pressure on a few teeth.

[Kita]

Originally Posted by MikeTC

Thanks for the Replies

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.


I would still like to know what damage is caused to the gears. I can only guess it lack of oil while there is a inconsistent pressure on a few teeth.

I don't believe it would be inconsistent pressure but I suppose you could call it that. it's more the rattle back and forth as the prop bangs back and forth and the backlash in the gears is bang back and forth over a long period of time. Pitting on the gears or possibly maybe even breaking a tooth off or a crack but I would suspect damage to the gear from banging back and forth over a long period of time.

[a64pilot]

Originally Posted by sailcrazy

We have a Autoprop on our monohull, with the KBW20 transmission. The autoprop is supossed to feather and stop-but it never has! The only way I can keep the driveshaft from spinning is to leave it in gear (Fwd or Rvs). Once I put it back in Neutral, the shaft slowly begins to spin, and stays spinning-without any eng-driven lub taking place, only splash lub from the rotation (I'm guessing). Is it really better to leave it in Neutral, and spinning, when the eng is off?

I have a KBW 20 on my IP with an Autoprop, if it spins, it does so slowly.
However Island Packet in the boats manual recommends sailing with the transmission in reverse to keep the (fixed) prop from spinning.
It’s my belief and apparently Island Packets as well that reverse won’t hurt the transmission. I believe their recommendation was based on eliminating the noise and vibration from a spinning prop, nothing else.
They way that a transmission would be damaged is by the clutch slipping, if you had hydraulic clutch packs or a cone clutch or any other design that uses engine torque to lock the clutch, then don’t sail with it in gear.
Our old KBW20 transmission use manually operated multi plate wet clutch packs, like a motorcycle if you have ever taken one of those apart.
In my opinion if the clutch doesn’t slip on our transmissions being engine driven, then it won’t by water pressure under sail.
However a hydraulically operated transmission and a cone clutch are different of course.

I believe our KBW20’s are lubricated by splash only, I don’t believe there is a pump. However I believe some have a cooler, and if that is true, then there has to be a pump?

Looking at the overhaul manual, I can find no pump, but there is a statement that says that clutch pressure is automatically applied in relation to output torque, so maybe being helical gears, they use the thrust to tighten the clutch packs?

Heck with it, IP says sail with it in reverse, I’m going with that.

[shawndear]

The saildrive oil and engine oil are separate. If in neutral all the lower parts will spin but the upper part wont (past the clutch). If placed in reverse, the prop doesn't spin, or spins very slowly, so no or little wear and tear in my mind. So yet another reason for leaving it in gear.

[CAR54]

I have the original owners manuel for the J28 that I sail. It has a Yamar 2GM20F engine and a Kanzaki model KM2P reduction gear with a 2 blade folding prop as orginal equipment. Now in its 6th season with me I have always s followed the operating instructions by Yamar which state when sailing place shifter into reverse gear.

The boat is now 30 years old and the engine and reduction gears are original.

[RonRicco]

I guess I will continue with the thread creep, but I have flexofolds with my SD20. Have used the GoPro to check them out underway and they have always been folded.

[expatria]

Mid-October I'll be taking delivery of my Xp38 with the Yanmar 29hp and twin bladed folding prop, which probably has the SD20 saildrive. I googled the issue and on the Kiwi Prop website there seem to be some good comments re this SD20 saildrive. It has a 'Dog Clutch', which ie can cause extreme wear if idling at over 850rpm, as this is not a 'slipping' clutch. Could this possibly lead to something?
On my current boat I have a Yanmar 15hp with shaft and folding prop and we always put it in reverse when sailing.

[MikeTC]

My original question was. "Why does Yanmar recommend leaving SD20 in neutral while sailing"? It may damage the gears / saildrive. How? The

[RichKiddy]

Originally Posted by contrail

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.

Surely, if it's not spinning, then it doesn't matter if it's in gear or neutral while sailing, so to stop the prop, don't fuss about sailing slowly, just stop the engine, in gear, and they will fold. Just remember to go to neutral afterwards, but certainly before starting.

[rancher44]

Iam still totally confused !!

[zippy]

Originally Posted by 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.

The prop shaft will spin much faster when motoring at 6 knots than it will when sailing at any speed you boat could ever do.

[earthmover]

Good that you posed the question. I charter cats in the Grenadines and this subject always comes up.