Put engine in reverse when sailing?

dolabriform

dolabriform

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freewheeling.world
Hi all

I have a Volvo Penta MD2001 with a sail drive, and heard the prop spinning whilst sailing for the first time at the weekend. First time it's been quiet enough to notice. It's really annoying!

I know the manual says not to put the gearbox in reverse, but in reality how much damage will it do ? A little? a Lot?

It's so satisfying when it stops spinning and there is silence all around :)

Thanks

David
 
I've been known to do this on my 2003 for the same reason. On occasion, it's reluctant to go into neutral, so I have to start in astern, but it immediately frees up. I can't see what damage it would do, unless the box relies on oil pressure to engage the clutches, but even then..?
 
I have a Volvo MD2030, not saildrive, fixed 3 blade prop.
The manual says to leave a fixed prop in neutral when sailing and a folding prop in reverse.
Despite that, since that engine was installed in 1995, practice has been to put the gearbox in reverse to prevent the prop freewheeling. The silence is very nice.
No damage has been observed, and the gearbox and engine have performed well during all those hours.

It's another whole argument as to whether the locked or freewheeling prop increases or decreases drag. I have two papers that totally contradict each other on that question.
 
KellysEye said:
Put the engine in gear the prop will stop and you will have successfully created prop drag.
Click to expand...

Back in the 70's and 80' I was privileged to be one of a regular cross channel race crew, whose successes featured weekly in Yachts & Yachting- in fact we were miffed if we did not get a podium place in JOG, each week.

We used to engage engine gear, forward or reverse (can't remember which), so it didn't seem to cause us too much delay or we would have abandoned that tactic :)
 
KellysEye said:
Put the engine in gear the prop will stop and you will have successfully created prop drag.
Click to expand...

Not according to people who really know in Southampton - it depends on speed through water as to whether it gives more or less drag.
For most sailboats, at their normal cruising speeds, a locked prop will produce slightly less drag, for folding and feathering props it's essential to make sure they feather.
Whether reverse or forward is another variable - for most boxes reverse is favourite, for my Autoprop with a Yanmar box, it's forward.
Marchaj covers the subject fairly thoroughly in one of his "Seaworthiness" books.
Really, a fixed prop on a sailboat is, IMHO, shows a serious lack of taste!!

More info here www.wumtia.soton.ac.uk/

PS One important point, some gearboxes need to have the engine running to work an internal oil pump - I'm happily ignorant about Volvo engines, and suggest that is a point that should be covered.
 
Last edited:
charles_reed said:
PS One important point, some gearboxes need to have the engine running to work an internal oil pump - I'm happily ignorant about Volvo engines, and suggest that is a point that should be covered.
Click to expand...

The volvo gearboxes are straightforward mechanical types. The official advice not to put in reverse with a fixed prop is widely ignored and does not seem to result in any harm.

PS You don't expect KellysEye to know about or take any notice of well researched evidence surely? If he did he would never have anything to say!
 
I find it difficult to understand why with a folding prop and sail drive it make an difference, at all, whether it is in forward or reverse.

We put ours into forward, because the gear/throttle lever is then less obtrusive
 
I have a VP2002.

The manual states let the prop spin. In a recent test, we mistakenly let the engine in gear, there was a 1/2 knot difference in speed. I commented to the crew his quiet it was and as we stopped the test (retuned the gear to the neutral position) you could feel the boat speed up.

My prop starts rotating at 5 kts which is both good and bad as I know we are making decent progress and it noisy.

Investigations are underway on the best prop to replace my current one and begging letters are being sent.
 
Here a question I wouldn't mind a answer to ,
120 sail drive , auto prop , why when I put it in rev the prop will continue spinning but in forward it locks ?
So far no Volvo dealer been able to answer the question , I been told it's not possible,
By the way the clutch doesn't slip .
Mine also won't go into neutral, I get around it by just a quick flick of the key , then put it in neutral and start , I doubt starting it in gear would do it any harm .
 
Why reverse? I put mine in ahead. Then, if I need to start the engine, she's moving ahead. I think the prop in gear must create additional drag but I feel a spinning prop increases the chance of something becoming entangled in it and that's more important than any trifling loss of speed.
 
The research I've seen and common sense indicate to me that there's more drag with the prop in gear. The noise in neutral is annoying though if you're trying to sleep.
 
KellysEye said:
Put the engine in gear the prop will stop and you will have successfully created prop drag.
Click to expand...

You will be surprised: a stationary prop actually creates less drag than a rotating one. The blades actually work as wings - moving through the water they generate "lift" that we use for propulsion. If the prop stops, the "wing" stalls - the flow separates from its surface - and "lift" (drag) gets substantially smaller. In aviation the aircraft fall from the sky...
 
Ideally, a 2-bladed prop should be locked vertically for least drag, so I am told, but really, it is much better to get a folding prop, even if it means selling the children to pay for it.
 
jiris said:
You will be surprised: a stationary prop actually creates less drag than a rotating one. The blades actually work as wings - moving through the water they generate "lift" that we use for propulsion. If the prop stops, the "wing" stalls - the flow separates from its surface - and "lift" (drag) gets substantially smaller. In aviation the aircraft fall from the sky...
Click to expand...

Unfortunately, it's not quite the same as a marine propeller will work with flat blades with no aerofoil section whereas a flat aircraft wing will really struggle because of the much lower density of air. I therefore doubt whether an aircraft wing stalling in air has much application to a marine propeller stalling in water. :)

Richard
 
If my folding prop is put in fwd when sailing it spins all the time due to the waterflow over the blades ,
so it is put in reverse and this stops the prop / gearbox from turning , therefore it is quiet , much better for the ears !
 
I too find the spinning prop in neutral a huge annoyance and something that spoils my sailing experience. Locking the prop by engaging fwd or reverse stops the prop but you can feel the extra turbulence on the rudder/tiller. And it's extra drag. Annoying...

I bought folding propellers for my last 2 boats: one a Flexofold, the other a Gori. Both were good, adding boatspeed by reducing drag, went well in fwd and reverse, were reliable and eliminated turbulence on the rudder.

If I were buying again I'd buy another Flexofold but remember with the Flexofold, when you finish motoring and you have your sails are up and pulling, you must return the throttle to neutral and, once the revs are down to tickover, just engage reverse for a moment to get the prop to turn in reverse and the blades to fold, otherwise the blades will stay open.

And when they are new, the Flexofold prop is a thing of beauty: ask anyone who has played with the props exhibited at the Southampton boat show. It's almost a shame to get them wet... :-)
 
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