Any risks from putting engine in reverse while sailing?

[RichardS]

Me too and for much longer than 12 years - this comes as quite a surprise - where can we see this advise from Yanmar ?

See post #10 for Yanmar bulletin.

Richard

 

[Simondjuk]

I'm pretty sure the manual for my Volvo 2030 with saildrive states that astern should be selected if a folding prop is fitted and the transmission left in neutral with a fixed prop.

I can also confirm that neutral is difficult to select prior to starting the engine if one sails with astern selected and a fixed prop fitted.

Discovering the latter prompted me to read up and find the former.

 

[Steve C Cronin]

I have been sailing with my GM gearbox in reverse for the past 12 years and this is the first time I have ever heard that it should not be done. Forward gear does nothing, prop still revolves. I start the engine with gear still in reverse, then shift into neutral.

My last boat had a 2GM20FW Yanmar (shaft & P bracket) and the manual said to lock the prop in reverse. Current boat with a Volvo says let it spin (saildrive) They were both correct for the health of their respective transmissions but as to drag (here we go again!) I believe that pulling a locked prop through the water, once a "cavitation-like" situation is achieved, causes less drag than a freewheeling one.

 

[vyv_cox]

but as to drag (here we go again!) I believe that pulling a locked prop through the water, once a "cavitation-like" situation is achieved, causes less drag than a freewheeling one.

Someone at a Scottish Engineering University researched this for a degree thesis and the results were reprinted in PBO a few years ago. He found most conclusively that letting a fixed type prop rotate caused far less drag than leaving it in gear. Maine Sail did a good bit of research himself, using a towed catamaran as a raft, and found just the same thing. I don't have the first report with me here but the second is at. http://www.catamaransite.com/propeller_drag_test.html

 

[DJE]

I have exactly the same set up as the OP on my boat (and a conventional two-blade prop) I usually leave the prop spinning but if I get fed up with the noise or someone is trying to sleep in the quarter berth I put it in reverse to stop the spin. No problem getting it back into neutral so far.

But I have often found that when the prop is spinning after shutting the engine down I can stop it by selecting reverse briefly then going back to neutral and it doesn't start to spin again. There must be just enough friction to hold it in place or the flow has become turbulent around the stalled blades so they are not generating any lift. Best of both worlds, prop stopped and engine in neutral.

 

[Salty John]

Here's what I found out when I researched the subject last year:

http://saltyjohn.blogspot.co.uk/2013/07/propellers-what-drag.html

 

[BlueSkyNick]

The simple answer to all this is to get a folding prop ! Apart from the initial investment, there are no downsides.

 

[vyv_cox]

The simple answer to all this is to get a folding prop ! Apart from the initial investment, there are no downsides.

I won't argue, although I have read plenty of adverse comments about folding props going astern. However, if I stop my Autoprop by selecting reverse, then go back to neutral, it will resume rotating.

 

[RAI]

I won't argue, although I have read plenty of adverse comments about folding props going astern. However, if I stop my Autoprop by selecting reverse, then go back to neutral, it will resume rotating.

Ah! Good to hear that. The Autoprop was on my wish list should my Maxprop go toes up. It seems such a neat design solution.

 

[prv]

I have read plenty of adverse comments about folding props going astern.

No complaints at all with ours, although our massive Volvo three-bladed curvy thing is a far cry from the old tiny two-blade egg-whisks.

Pete

 

[Tranona]

No complaints at all with ours, although our massive Volvo three-bladed curvy thing is a far cry from the old tiny two-blade egg-whisks.

Pete

Agree. Before fitting my FlexoFold 2 blade we carried out a lot of back to back tests (for another project) with a variety of different designs of props against the standard 2 blade fixed (on a saildrive). Apart from the slight lag when the blades open in reverse, performance in all other respects (speed, stopping distance, bollard pull) was the same for the fixed or the folder. Blade size and shape has a big influence on performance.

 

[capnsensible]

Reference is here.....

http://www.seawindcats.com/system/f... position during sail with engine stopped.pdf

Many thanks.

 

[rotrax]

Island Packet invariably use Yanmar engines-all shaft.

It is recomended that astern is selected when sailing.

The IPHOMEPORT owners website often has owners asking how to alleviate the difficulty of selecting neutral after sailing with the astern gear engaged.

IIRC the answer is to disconnect the safety switch behind the gear/speed control which allows starting in astern, and from there it is easy to select neutral or ahead.

Our engine, a 3JH2 series, despite having well in excess of 3500 hours on it does not suffer this problem-neutral can be found reliably.

We use a Kiwi Prop. We were on the Haslar Sealift yesterday for a pre season bottom scrub, anode change and grease the Kiwi Prop.

Away in under an hour, £140.00. The prop just needed a light clean. When my old Wanner grease gun pumped in the fresh lube it was only moments before the old grease was pushed out.

I know there are one or two adverse comments about Kiwi Props on here from time to time, but our is undoubtedly on of the best purchases we have made.