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Old 13-06-2015, 07:15   #1
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Folding Prop and SD20 - neutral or reverse?

At the risk of stirring up the "let her spin" versus "lock her in reverse" debate started, I thought I'd ask the question just within the context of one scenario, mine . I have a Yanmar SD20 Saildrive with a two blade folding propeller. The concensus opinion has definitely been to put it in reverse when sailing with the engine off so that with it locked in gear the prop will fold and it will cause less drag. However, the manual for the SD20 clearly states to leave it in neutral (see attached picture). I can understand if I had a non-folding prop that you would want it to spin, but with a folding prop I'd think reverse woiuld be the best option. Although I don't want to go against the manual. Anyone else out there with a similar setup have any thoughts? Anyone with an SD20 and folding props talked to Yanmar about it by any chance?

Thanks,
Zoid
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Old 13-06-2015, 07:21   #2
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Re: Folding Prop and SD20 - neutral or reverse?

We always left ours in neutral Kenny. Recently we heard a whirring sound from the aft berth and tracked it down to the spinning saildrives the prop hadn't folded and was spinning the shaft. We selected fwd for 20 seconds, the prop folded and back to neutral again. Maybe the prop needed a clean as normally it folds as soon as we cut the engine.
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Old 13-06-2015, 08:52   #3
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Re: Folding Prop and SD20 - neutral or reverse?

Reverse will be fine with a folding prop. The SD20 uses a dog clutch, so I don't know what slipping they are expecting.

If folders do not fold, it is best to shift into reverse rather than forward. Forward gives the possibility of either turning the engine or slipping the cone clutch (if that type).

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Old 13-06-2015, 09:10   #4
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Re: Folding Prop and SD20 - neutral or reverse?

Like Mark said, dog clutches don't slip, hence no more wear on the clutch than normal putting it in/out of gear.

IMO, forward or reverse doesn't matter, the engine has way too much compression for the prop to turn it over. I run fixed 2 blade props and I lock mine in forward as it keeps the throttle controls in a more comfortable position.
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Old 14-06-2015, 08:56   #5
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Re: Folding Prop and SD20 - neutral or reverse?

Quote:
Originally Posted by Zoid View Post
At the risk of stirring up the "let her spin" versus "lock her in reverse" debate started, I thought I'd ask the question just within the context of one scenario, mine . I have a Yanmar SD20 Saildrive with a two blade folding propeller. The concensus opinion has definitely been to put it in reverse when sailing with the engine off so that with it locked in gear the prop will fold and it will cause less drag. However, the manual for the SD20 clearly states to leave it in neutral (see attached picture). I can understand if I had a non-folding prop that you would want it to spin, but with a folding prop I'd think reverse woiuld be the best option. Although I don't want to go against the manual. Anyone else out there with a similar setup have any thoughts? Anyone with an SD20 and folding props talked to Yanmar about it by any chance?

Thanks,
Zoid
The SD20 manual refers to a fixed prop. There is an Yanmar bulletin that clarifies that with a folding prop you may put the gear in reverse to help the prop to close.
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Old 14-06-2015, 09:08   #6
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Re: Folding Prop and SD20 - neutral or reverse?

Because of this ongoing debate I have spoken to Yanmar's technical staff personally.
They remain adamant that keeping a saildrive in gear while sailing will negate any warranty.... non folding or folding prop.
I have flexofolds and they advise to temporally put gear in reverse when starting to sail only long enough for props to fold then neutral.
How a folding prop would cause damage is puzzling to say the least. I have sailed this way for years and the props stay folded so no big deal.
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Old 14-06-2015, 09:57   #7
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Re: Folding Prop and SD20 - neutral or reverse?

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Originally Posted by caradow View Post
Because of this ongoing debate I have spoken to Yanmar's technical staff personally.
They remain adamant that keeping a saildrive in gear while sailing will negate any warranty.... non folding or folding prop.
I have flexofolds and they advise to temporally put gear in reverse when starting to sail only long enough for props to fold then neutral.
How a folding prop would cause damage is puzzling to say the least. I have sailed this way for years and the props stay folded so no big deal.
Correct - this is the formal Yanmar's statement in the bulletin I have referred to above.
However, once the folding prop is folded, the gear position doesn't matter much, only in my opinion of course.
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Old 14-06-2015, 13:31   #8
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Re: Folding Prop and SD20 - neutral or reverse?

Again, note that the problem with clutch slippage is with the cone clutches on the SD40-50. The SD20 uses a dog clutch, so should have no issue being locked in reverse.

The cone issues on the SD40-50 are so bad and notorious that Yanmar's sensitivity to leaving them in reverse with a folding prop is most likely a CYA thing that gives them plausible deniability.

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Old 14-06-2015, 15:06   #9
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Re: Folding Prop and SD20 - neutral or reverse?

we have a Bukh Diesel Saildrive with a Gori folding prop and always have the engine in neutral when sailing. We have never noticed a prop noise when under way.
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Old 14-06-2015, 15:40   #10
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Re: Folding Prop and SD20 - neutral or reverse?

I read the Yanmar tech notice posted by Meirriba. On page 2-2 at the very bottom it states the above positions are for less than 3 kts. What about when sailing faster ???
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Old 14-06-2015, 21:37   #11
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Re: Folding Prop and SD20 - neutral or reverse?

Use your heads, folks! ONCE FOLDED, a folding prop exerts zero torque upon the propshaft. Zero... just like a fixed prop when the boat is not moving.

I don't know what the Yanmar guys are on about, but I can't see how the tranny can be harmed no matter what position the shift lever is in.

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Old 14-06-2015, 23:03   #12
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Re: Folding Prop and SD20 - neutral or reverse?

Quote:
Originally Posted by wannacat View Post
I read the Yanmar tech notice posted by Meirriba. On page 2-2 at the very bottom it states the above positions are for less than 3 kts. What about when sailing faster ???
No. They mean only to do the action of gear change in slow speed. However this may be impossible or inconvenient, because you kill engine and start sailing when the wind picks up and boat sail faster. This comment looks to me like a sort of ass cover on Yanmar's side.
But - I do not think an Yanmar executive will be around to check when exactly you have changed gear to reverse in order to fold your prop.
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Old 15-06-2015, 02:03   #13
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Re: Folding Prop and SD20 - neutral or reverse?

Thanks everyone, definitely appreciate the feedback!

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Old 15-06-2015, 02:42   #14
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Re: Folding Prop and SD20 - neutral or reverse?

As DotDun says, forward or reverse doesn't matter. When I had a folder on my SD20 I would put it in reverse without any problems for years. If I forgot to put it in gear when sailing, the propellor could spin. Now I have replaced the folder with a Kiwi Feathering Prop. It is 3 bladed and the blades automatically feather with the water flow. With this prop the instructions are to leave the motor in neutral. Incidentally I feel the Kiwi has less drag than a folder which may not close properly sailing at slow speeds which could be why a folder can spin if not locked in gear. Once a folder starts spinning the centrifugal force of the weighted blade ends keep it open. So put it in gear before that happens.
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Old 15-06-2015, 03:02   #15
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Re: Folding Prop and SD20 - neutral or reverse?

Further to my comments about folding props. Keen racing types around here have been known to dive overboard before a race and put rubber bands around the blades of folding props to ensure they dont open and cause unnecessary drag. After the race when the motor is started, the rubber band breaks away. You could try that.
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