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Prop loose on shaft?

webcraft

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8 Jul 2001
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Cyberspace
Engine is very poorly and out of the boat.

Cleaning out the empty space today I casually twirled the coupling. Seems like there is a couple of degrees play in both directions before the prop turns.

Is the prop loose on the shaft, and if so why? Don't want to add a Cascais liftout to the cost of fixing the engine. (Plan is to have a wee sail around the Algarve then lift out at Bruce's if there is space, so will fix wonky props etc then, but will it fall off before then?)

- W
 

jamie N

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20 Dec 2012
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Fortrose
How do you know that the prop's turning a couple of degs after, so to speak, if the boat's wet?
For me though, have a drink and forget about it.
 

sailorman

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21 May 2003
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77,841
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Here or there
is a feathering prop, as one can give the shaft a sharp twist but the blades lag a bit then move, perhaps giving the feel of a loose prop
 

mjcoon

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18 Jun 2011
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3,101
Location
Berkshire, UK
Engine is very poorly and out of the boat.

Cleaning out the empty space today I casually twirled the coupling. Seems like there is a couple of degrees play in both directions before the prop turns.

Is the prop loose on the shaft, and if so why? Don't want to add a Cascais liftout to the cost of fixing the engine. (Plan is to have a wee sail around the Algarve then lift out at Bruce's if there is space, so will fix wonky props etc then, but will it fall off before then?)

- W
Can't answer your question. But decades ago was motoring south to the Lefkas ferry/bridge when the engine started to sound a bit different. Only two of us aboard who discussed and then speculated maybe we just had something wrapped round the prop and perhaps running briefly in reverse would shift it. But in reality the shaft coupling was loose and reverse just put a pull on the shaft instead of push, and wound the shaft out of the coupling so losing our drive altogether. Being on flotilla we summoned the lead boat to come back and sort it. We did not even have a hex key to tighten the coupling. The lead boat were kind enough to suggest that we did not lose the shaft since they did not have spares! Not to mention the hole that would be left in our boat. But of course the rudder would in practice have prevented that. We put up our sails just to make ourselves more visible. (No GPS fixes back then!) Anyway the lead boat roared up kitted out with wet suits ready to shove the shaft back in and tighten the coupling. I think we even made the opening time of the Lefkas canal...
 

jamie N

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20 Dec 2012
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Fortrose
I wish. No, a big 3-blader I locknutted and loctited before launch.

- W
That's a concern isn't it, as (I'm guessing) you can feel that there's been an alteration since you fitted it, when of course it didn't have any movement.
Not being funny, but is the prop R/H or L/H? If it's R/H, it'll always be trying to wind itself 'up' the shaft, and would (for me) be less of an immediate concern, in that it's not going to stuff you right now.
Perhaps this would allow you time with confidence, to get to the stop where you can inspect properly?
 

Rappey

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13 Dec 2019
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1,548
I had mine wear at the other end where the coupling flange fits on the shaft.
 

jamie N

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20 Dec 2012
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Fortrose
Actually, I might be thinking back to front?
I ask, if the engine's turning R/H (clockwise), it's going to be 'unwinding' a prop potentially, isn't it?
Apologies for the confusion created with that.
However, in my experience it tends to be the change of direction on the shaft that causes wear on the 'woodruff key' and movement of the prop.
I'd not worry about it, but'd get it looked at when the opportunity presents itself.
 

bikedaft

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16 Dec 2008
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tayvallich
Actually, I might be thinking back to front?
I ask, if the engine's turning R/H (clockwise), it's going to be 'unwinding' a prop potentially, isn't it?
Apologies for the confusion created with that.
However, in my experience it tends to be the change of direction on the shaft that causes wear on the 'woodruff key' and movement of the prop.
I'd not worry about it, but'd get it looked at when the opportunity presents itself.
You have to go swimming (guess how i know that ☺)
 

wully1

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Joined
27 Aug 2002
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2,180
Location
west coast of Scotland
Can’t think why the prop would suddenly be loose on the shaft if it was correctly keyed and mounted..

The shaft couldn’t be rattling around in a badly worn cutlass bearing?
 

Topcat47

Active member
Joined
2 Jun 2005
Messages
4,705
Location
Solent, UK
Personally I wouldn't rely on locktite alone on a prop nut. I've owned my boat for many years and I've never had a prop nut move, or a woodruff key wear. I HAVE changed from a castellated nut and split pin to a plain nut with a soft iron tab washer ( I lost the original). I would expect you to be able to feel if the prop is loose on the shaft and my guess would be a loose prop nut. Were it me, I'd dive down and see if the prop was wobbly on the shaft. If the gearbox is still in place, it is possible that you are getting a little play in the backlash of the gearbox and that's what you're feeling at the coupling. These are cheaply checked before you think about lifting out.
 

Plomong

Active member
Joined
7 Feb 2006
Messages
1,908
Location
Bilbo, Spain (Basque Country, actually)
Engine is very poorly and out of the boat.

Cleaning out the empty space today I casually twirled the coupling. Seems like there is a couple of degrees play in both directions before the prop turns.

Is the prop loose on the shaft, and if so why? Don't want to add a Cascais liftout to the cost of fixing the engine. (Plan is to have a wee sail around the Algarve then lift out at Bruce's if there is space, so will fix wonky props etc then, but will it fall off before then?)

- W
Is there an anode on the shaft ? It might be loose and flailing about.

Plomong
 
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