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Curmudgeon

Propshaft turning at idle

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I am new to owning a narrowboat and to engines in general so apologies if this seems a silly question. When my engine is running and the gearbox is in neutral if I lift the engine hatch you can see the propshaft turning very slowly / lazily. Any movement of the controller forward or back clearly engages the gears in the appropriate direction and the movement increases accordingly. Should the propshaft be completely still in neutral? Or do they just sometimes have some movement in them?

Any advice much appreciated.

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It very much depends on what type of gearbox it is.

For certain types, I would say it is almost inevitable - for others probably less so.

Do you know what you have, (and on what engine).

If it is only turning lazily it is not likely to be that much of a problem, but the oat will of course creep forward (or backwards?) slowly if not restrained.

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My Lister SR2 decided to do this a couple of years back. As I do must of my boating singlehanding it was disconcerting to see it leave a lock on its own and I had to do a dramatic leap from the towpath before it disappeared without me, albeit at a very slow pace.

Turned out the gearbox need an adjustment which took less time than undoing the bolts that held the cover on, but it still took me a while to find an engineer who knew what to do - the one RCR sent out refused even to look at it, even though I waved the manual under his nose.

In other words, we do need to know engine and gearbox type before anyone can answer questions like this - too much information is better than too little.

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13 minutes ago, Curmudgeon said:

I am new to owning a narrowboat and to engines in general so apologies if this seems a silly question. When my engine is running and the gearbox is in neutral if I lift the engine hatch you can see the propshaft turning very slowly / lazily. Any movement of the controller forward or back clearly engages the gears in the appropriate direction and the movement increases accordingly. Should the propshaft be completely still in neutral? Or do they just sometimes have some movement in them?

Any advice much appreciated.

Some do some dont. I doubt its a problem. My present doesnt but some previous have.

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17 minutes ago, Arthur Marshall said:

In other words, we do need to know engine and gearbox type before anyone can answer questions like this - too much information is better than too little.

 

Gearbox type in particular. Engine is less important, irrelevant even. 

If you can't see a make and model marked on the gearbox, a photo will be just as good. It will be instantly recognised, probably.

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11 minutes ago, Mike the Boilerman said:

 

Gearbox type in particular. Engine is less important, irrelevant even.

Not necessarily entirely so......

The same gearbox may "creep" if the engine driving it idles at 1000 rpm (say), but may not creep if the engine driving it only idles at 400 rpm (say).

So it might, be relevant.

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2 minutes ago, alan_fincher said:

Not necessarily entirely so......

The same gearbox may "creep" if the engine driving it idles at 1000 rpm (say), but may not creep if the engine driving it only idles at 400 rpm (say).

So it might, be relevant.

 

Yes, but once the make and model of gearbox is known, if it is one where some drag is normal the OP can be reassured it is normal for his box. If it a box where there should be no drag, then he will know there is something wrong with his. Neither of these possibilities depends on the engine. 

 

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Its most likely just oil drag in the gearbox, a very slowly turning prop needs very little force (oops torque) so the drag might turn it, its very unlikely to cause the boat to move forwards to a noticeable extent. Stick yer foot on it, that'll stop it.

...........Dave

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My Barrus with a PRM gearbox and centaflex has always done that, no real problem. In fact came in quite useful once when my control cable snapped as I managed to travel very slowly for  about a mile to some acceptable moorings  twas a very still day though. 

Not too sure that I personally would tighten the stern gland to stop it is as this might end up with stern gland being over tightened, thus solving a non problem by introducing a potential problem. 

Edited by reg

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Thanks for the quick responses. Of course I should have cited the make & model. It is a PRM150 with a Beta 43 engine. As far as I can tell the amount of movement isn’t sufficient to actually move the boat forward. From what most people have said it sounds as though it isn’t anything to worry about unduly.

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5 minutes ago, Curmudgeon said:

Thanks for the quick responses. Of course I should have cited the make & model. It is a PRM150 with a Beta 43 engine. As far as I can tell the amount of movement isn’t sufficient to actually move the boat forward. From what most people have said it sounds as though it isn’t anything to worry about unduly.

Same engine and gear box. Mine does the same but not noticed the boat moving forwards.

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3 minutes ago, Curmudgeon said:

From what most people have said it sounds as though it isn’t anything to worry about unduly.

That I think is the correct conclusion. 

Appreciate that being new to narrow boats it can be a bit difficult to know what to worry about and what not to worry about. 

The one area to keep a close watch on is the stern gland and packing, regular maintenance is required in this area. Also test your bilge pump as often as possible 

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37 minutes ago, Curmudgeon said:

Thanks for the quick responses. Of course I should have cited the make & model. It is a PRM150 with a Beta 43 engine. As far as I can tell the amount of movement isn’t sufficient to actually move the boat forward. From what most people have said it sounds as though it isn’t anything to worry about unduly.

 

30 minutes ago, Dr Bob said:

Same engine and gear box. Mine does the same but not noticed the boat moving forwards.

I also have that somewhat ubiquitous engine and gearbox combination.  I get no shaft rotation in neutral even with a low friction Volvo stern seal.

Now we know the gearbox,  perhaps we need a poll!

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1 hour ago, Curmudgeon said:

Thanks for the quick responses. Of course I should have cited the make & model. It is a PRM150 with a Beta 43 engine. As far as I can tell the amount of movement isn’t sufficient to actually move the boat forward. From what most people have said it sounds as though it isn’t anything to worry about unduly.

So it’s just the oil between the clutch plates causing a little drag, will be more obvious when cold; and may not happen at all when warm. All pretty normal for that box and others of its type.

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Consensus seems to be that it is not that uncommon or alarming and I can go on to find the next thing that needs worrying about. Do appreciate everyone's input.

  • Greenie 1

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3 minutes ago, Curmudgeon said:

....and I can go on to find the next thing that needs worrying about.

Do pop back if you need some suggestions...! ;)

 

(Start with your battery charging regime) 

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Perkins 4108 with PRM 150. Most of the time my propshaft is perfectly still, just occasionally the propshaft does turn in neutral. I decided a while ago that it was nothing to be concerned about.

Kevin 

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All motorcycles i have owned will turn the back wheel when placed on a centre stand with gearbox in neutral and engine idling, just drag in the gearbox.

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8 hours ago, Sea Dog said:

 

I also have that somewhat ubiquitous engine and gearbox combination.  I get no shaft rotation in neutral even with a low friction Volvo stern seal.

Now we know the gearbox,  perhaps we need a poll!

I guess mine is induced rotation from coupling with the ecofan.

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1 minute ago, Dr Bob said:

I guess mine is induced rotation from coupling with the ecofan.

Maybe you're moored on a fast flowing river? Have a look out of the window... 

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If you jack up a car to have the driving wheels off the road and rev the engine the wheels go round.

.............Dave

 

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12 minutes ago, Sea Dog said:

Maybe you're moored on a fast flowing river? Have a look out of the window... 

Bit cloudy. Branches are blowing in the wind a bit. Looks like I might need a coat on today?

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just be grateful you were not the chief engineer on HMS Queen Elizabeth during her trials when the thrust block on one of her 2 propshafts started to disintegrate.  (last night on C4).

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