Volvo MS2L gearbox. OK to freewheel or not.

MM5AHO

MM5AHO

Well-Known Member
Joined
1 Oct 2007
Messages
2,553
Location
Central Scotland
Visit site
Can't find any reference in the manual for this. It's said that drag from the prop (3 blade fixed) is greater with prop locked.
But freewheeling it depends on manufacturers recommendation.

Is this prop Ok to freewheel?

(MD2030 with MS2L gearbox in Rival 32.)
 
I would have thought so. Locking the prop creates a lot of load on the gearbox, and you can do damage to it trying to unlock it before you start the engine.
 
I reckon that generally it is best to let the prop rotate with the gearbox in neutral unless your engine manufacturer specifically recommends locking it, usually because of a wear issue caused by limited oil circulation.

If you wish to lock the prop to reduce the gearbox noise then fit a shaft brake and accept the slightly higher drag from a locked fixed prop. Not possible with saildrives of course.

Richard
 
MM5AHO said:
Can't find any reference in the manual for this. It's said that drag from the prop (3 blade fixed) is greater with prop locked.
But freewheeling it depends on manufacturers recommendation.

Is this prop Ok to freewheel?

(MD2030 with MS2L gearbox in Rival 32.)
Click to expand...


The owners manual for the engine says

When under sail the control lever should be in the neutral position if the propeller is a fixed propeller. If the propeller is a folding propeller the control lever should be in the reverse position. Start the engine and run for five minutes every ten hours when on long-distance cruises
Click to expand...

I imagine the reason for running the engine briefly every 10 hours is to ensure lubrication of the top gearbox bearing and possibly also the top ( forward ??) pinion gear.

There is no distinction made between the MS2 gearboxes and the 120S drive which is not surprising because the upper gearbox of the 120S drive is a very similar design to the MS2 gearboxes.
 
Thanks for that info.
I didn't see that in my manual, I'll have another read.!
Engine installed in about 1990? and sailed with gearbox in reverse since!
Its the drag I'm trying to reduce.
 
Thanks Vic,

I don't have that manual, I have only a workshop manual.
Perfect for setting tappets, assembling little ends etc, but not much use in general operating instructions.
 
MM5AHO said:
Can't find any reference in the manual for this. It's said that drag from the prop (3 blade fixed) is greater with prop locked.
But freewheeling it depends on manufacturers recommendation.

Is this prop Ok to freewheel?

(MD2030 with MS2L gearbox in Rival 32.)
Click to expand...
Ive posted this before many times. When I had my first Bene, it had a 2030 exactly the same. the shaft used to spin. I phoned VP up, spoke to their techie. He said VP used to advise sticking in reverse, however it could get jammed in gear, the answer to this was to flick the starter motor and it was then possible for neutral to be selected. Apparantly owners couldnt manage this so they then advised to leave spinning!
S
 
We have a MS2L and with a fixed prop you definitely need it to spin. However Volvo don't like this much as without the engine going the cooling isn't going through the gearbox so they cover their backside by saying you occasionally need to start the engine. I don't know anyone who does.
However we replaced our fixed prop with a feathering Maxprop and would definitely recommend it. Not only is the drag much reduced, the noise is less and engine performance significantly improved (You can fit a larger prop as it doesn't matter anymore).
We briefly put the gearbox into reverse to feather the prop and then put it back into neutral. This saves the embarrassment of starting the engine whilst in reverse as you usually forget.
 
pandroid said:
We have a MS2L and with a fixed prop you definitely need it to spin. However Volvo don't like this much as without the engine going the cooling isn't going through the gearbox so they cover their backside by saying you occasionally need to start the engine.
Click to expand...

I am surprised it need any cooling when just free wheeling. Do VP actually say this is the reason they recommend running the engine periodically.
I'd have thought lubrication of the top bearing was more likely to be the reason. I am sure I have read that somewhere.
 
I think the reason that my co-owner has always used "reverse" to stop the prop spinning is as a result of a very old test that showed that there was less drag by doing this as opposed to letting the prop spin. That and that a spinning prop makes some noise.
I can't imagine much heat being generated in a spinning prop gearbox either, but next month will do some investigation when sailing north to Orkney.

I must dig out the report on "fixed prop means less drag" and post it.
The much more recent one by one of the magazines seems a lot more definitive.
The idea of a feathering prop appeals, and will be investigated this winter. That same report has good data on comparisons between different types available.
 
There are a least three reports showing that a spinning prop causes less drag than a fixed one

1. The first AFAIK was a thesis done by a man at Glasgow(?) uni. I have a link on the laptop, available tomorrow. A summary of this was printed in PBO
2. Independent tests carried out for YM by Emrhys Barrell, includes various graphs of fixed, folding and feathering props at various speeds.
3. Maine Sail in USA measured the lever effect of fixed and rotating prop on a towed catamaran.

All three agree findings, for lowest drag allow the prop to rotate. The YM report amplified these findings by showing that, as might be expected, a folding prop offers the lowest drag, a feathering one only slightly higher, a rotating prop a good deal more and a fixed one a lot more.

Interesting situation with my Autoprop. If I put the gear in neutral the prop continues to turn, presumably with the blades presenting some area to the flow, and hence some drag. Putting the gear in reverse stops the rotation, feathers the blades and the speed increases noticeably.
 
Last edited:
The copy I have (at home, and I'm not there) is so old it was copied with one of those Photostat machines (heat sensitive paper) predecessor to today's electrostatic photocopier.
It might have been a magazine article, and Glasgow sounds familiar, but maybe my reading of that is as poor as my reading of a manual?
It must be true though, that a rotating fixed prop produces much more drag than a feathering or folding type? It might be less than a stationary fixed prop, but there is some force required to rotate it, so that must come from drag.

Vyv, is there a typo in what you wrote in last 2 lines? Was your second "neutral" meant to be "gear"?
 
MM5AHO said:
Vyv, is there a typo in what you wrote in last 2 lines? Was your second "neutral" meant to be "gear"?
Click to expand...

Sorry, you are right, I have corrected it. On the Yanmar putting it into reverse locks the shaft whereas forward does not. As Skipper Stu wrote earlier this locks the control and it is not possible to go back into neutral until the engine is turning over. Rather than blip the starter motor we just start the engine on tickover, which does it no harm (up to now, 2300 hours, which I was amazed to discover is close on 100,000 miles in car terms. I still think of it as a new engine, the original silver paint remains on the hoses)
 
MM5AHO said:
I think the reason that my co-owner has always used "reverse" to stop the prop spinning is as a result of a very old test that showed that there was less drag by doing this as opposed to letting the prop spin. That and that a spinning prop makes some noise.
I can't imagine much heat being generated in a spinning prop gearbox either, but next month will do some investigation when sailing north to Orkney.

I must dig out the report on "fixed prop means less drag" and post it.
The much more recent one by one of the magazines seems a lot more definitive.
The idea of a feathering prop appeals, and will be investigated this winter. That same report has good data on comparisons between different types available.
Click to expand...

There can be a big difference between spinning freely and spinning a boat gearbox.
Traditional practice was to have a two blade prop and lock it in line with the keel.
 
vyv_cox said:
There are a least three reports showing that a spinning prop causes less drag than a fixed one

1. The first AFAIK was a thesis done by a man at Glasgow(?) uni. I have a link on the laptop, available tomorrow. A summary of this was printed in PBO
2. Independent tests carried out for YM by Emrhys Barrell, includes various graphs of fixed, folding and feathering props at various speeds.
3. Maine Sail in USA measured the lever effect of fixed and rotating prop on a towed catamaran.

All three agree findings, for lowest drag allow the prop to rotate. The YM report amplified these findings by showing that, as might be expected, a folding prop offers the lowest drag, a feathering one only slightly higher, a rotating prop a good deal more and a fixed one a lot more.

Interesting situation with my Autoprop. If I put the gear in neutral the prop continues to turn, presumably with the blades presenting some area to the flow, and hence some drag. Putting the gear in reverse stops the rotation, feathers the blades and the speed increases noticeably.
Click to expand...
All of these tests were done with rigs where the prop spins far more freely than a typical boat gearbox.
Sloppy stuff to fill the pages of our comics.
What's clear to me is that fixed three-blade props are a terrible idea for a proper sailing boat.
 
"Traditional practice was to have a two blade prop and lock it in line with the keel. "

But didn't this mainly apply to long keel boats where the keel formed a sort of shelter for the 2 bladed?
 
You must log in or register to reply here.

Share this page

Top