in gear or freewheeling

[petersto]

Whilst sailing on the weekend, lifted the engine hatch and found the shaft merrily turning. I am sure I have read somewhere this does not do the gearbox any good.
If this is the case what is the procedure for locking the shaft. I managed it by playing with the controls but once locked only way to release it was to start the engine. Didn't seem right somehow. The engine is a volvo md2c the boat is a centaur. I would greatly appreciate any advice.

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[snowleopard]

there are 2 reasons for locking the shaft: (a) it wears the bearings etc. (b) it causes drag: a free-spinning prop causes more drag than a locked one. and yes, it may not make sense but it's a proven fact!

just put it in gear before or after turning off.

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[jimi]

I just put mine in reverse when I've shut off the engine.

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[maris]

I have a piece of steel flat bar which I put through the gear box/propshaft coupling. This then lies against the engine bearer and stops the prop turning. On my westerly cirrus when the shaft/coupling keyway is on top the prop is sitting vertically behind the keel.
Some guys I spoken to about locking off props say they wrap rope round the shaft, they then tie of the loose end and this stops the shaft from turning. I've not tried this myself so I don't know if it works.

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[philip_stevens]

So what do you and the rope clan do when you need the engine in a great hurry - MOB and suchlike???

Putting the engine in gear is a better option.

Eric Hiscox (spelling) always left his gearbox in ahead gear in case he had to start it in a hurry. This way, it would be going ahead as soon as the revs came up. And the amount of sailing he did, he should have known.

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Philip

 

[Ivy]

I have a Volvo MD2010 with a sail drive leg, I always put it in reverse when sailing because if I put it in forward the prop will still turn, not as fast as when in neutral though

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[maris]

I have never been in a situation where I've had to use the engine in a hurry. With some forward planning and some common scence I don't think the problem of needing the engine in a hurry will ever come up.
I should add that I sail in the waters on the east side of Skye. No tankers, no ferries, one maybe two coasters a week. Miles of water with perhaps a fishing boat in the distance or a yacht on the horizon then again perhaps not.
As for MOB, deep sadness........ I sail solo.
I don't know about the rope boys........ panic possibly........ must ask.
Well done you for pointing this out. I suppose in busy waters the engine could be needed in a hurry.
I belive there are various clamps on the market for stopping shaft spin. They may release when the gear is engaged.

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[maris]

Who was or is Eric Hiscox? I do boats not books........... assuming he wrote a book. Anything writen in a book is usualy only someone elses opinion, it may not always be the best way.

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[Heckler]

have a volvo 2030 with an mds2? box and the same happens, spoke at great length with the vp tech, he saisd that vp used to recommend that you leave in reverse but people were finding out that it would jam and you had to flick it with the starter to make it disengage, so now their advice is let it spin, and that is official
stu

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[chas]

I have a hydralic gearbox which does not lock if neutral or reverse is selected. Compass gave me the answer to stopping the prop turning in the form of a freebie anchor shaped key ring. if necessary, I jam this beteeen the disk part of the shaft joint and a bit of gearbox. There is a line attached fed up to the cockpit. If the enegine is needed in an emergency, quick pull and the shaft is free!

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[quaelgeist2]

Apart from
a) the fact that this is an age old question which usually pops up during the long and boring winters....
b) some manufacturers do not give you a choice (e.g. Volvo Saildrives are not supposed to be freewheeled because of lubrication needs of the shafts)

There are some tests which do saw some seeds of doubt on the commonly held belief:
-Resistance of a 3 bladed prop FIXED: Cp=1,3
-Resistance of a 3 bladed prop FREEWHEELING: Cp=0,3
-Resistance of a 2 bladed FOLDING prop: Cp=0,06

(average calculations of several makes, but with little variation within the groups)
Above are only the resistances of the props, there is of course the question of the whole drive system, but this study focused on the prop as key element, or is it?

Using the resistances of above with a YD-40 yacht (approx. 7,8 to) and a typical speed of 6,8 kn sailing without resiatnce of a prop, then
reduction of the speed induced by
- fixed, 3 bladed prop: 6.8 to 6.0 kn
- freewheeling 3 bladed prop: 6.8 to 6.5 kn
- folding prop: 6.8 to 6.76 kn

At low speeds up to 1.5 kn appaears no significant difference between the props - no turbulence, but smooth flow around them?
=========
Personally, I have found the answer in a folding prop, which allows me sufficient speed in calm breezes and control in harbours - the rest I sail anyway. To maximize the effect I put the gear in reverse when sailing. If I forget it and start the engine in gear, then the voltage drops enough to reset the instruments!

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[Metabarca]

Re: starting/stopping in gear

This post leads on to another question. Does it do any harm to stop and to start the engine in gear? Does the starter work harder? Religiously, I always check I'm in neutral before starting up or shutting down, but that may just be a car-driver mentality! Any comments?

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[dickh]

Re: starting/stopping in gear

I must be honest and say that up until last year I regularly left the engine in forward gear and just started in gear. BUT I did have a problem at the end of the season with the gearbox not driving initially, stripped the gearbox, found nothing wrong, but replaced the clutch plates as a matter of course. Absolutely fine this year but since looking at the handbook(Hurth G/box), it recommends leaving it in reverse if you need to stop the prop turning.


<hr width=100% size=1>dickh
I'd rather be sailing... /forums/images/icons/smile.gif

 

[petersto]

Well as usual a great deal of advice(one of which I wouldnt say I fully understood and I cant afford a folding prop) and thank you all very much. However I thought perhaps someone would come up with the definitive advice. I do not like the sound of jamming the shaft by the time I had the grating up and opened the hatch thumbscrews anything could have happened and knowing my luck probably would have. My mate has a yanmar(moody 33) and he just selects forward and thats that when he wishes to start the engine he puts it in neutral and thats that.
I will have to go down this weekend and have another tinker. Thanks all anyway.

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[FinesseChris]

who was Eric Hiscox?

Only sailed round the world three times, or was it four...
More wisdom in Cruising under Sail than at a hundred club bars or a thousand bulletin boards!
Chris

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[richardandtracy]

Leave freewheeling...

And connect the shaft to a dynamo to charge the battery. Why throw a trailing generator over the back when you've already got the blades for one that could supply all the power you could desire?

Regards

Richard.

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[Plum]

Locking the prop while sailing will create less drag than a freewheeling one. However, as you have experienced, depending on the gearbox design, putting it in gear can either make it difficult to get it out again is sailing at a reasonable speed or does not lock the shaft at all. If you have these problems the only solution is some form of shaft brake to reduce drag and to reduce shaft wear. However, the brake has to be failsafe in case you try to start the engine with it engaged and has to be quick to disengage in an emergency, so in these cases letting it freewheel could be a reasonable compromise.

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[vyv_cox]

Does your mate check that the shaft does in fact stop when he puts the gearbox in forward? On my Yanmar GM30, putting it in forward has no effect at all. Putting it in reverse stops it from rotating. After a few hours like this it is almost impossible to move the gearlever without the engine running, so I normally start it in reverse and then put the lever into neutral.

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[ccscott49]

Anybody know how to stop a prop turning, with a borg warner velvet drive gearbox? Without the rope trick etc.

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[zefender]

Remove the oil and let it run for a week or two - that should sort it.

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