removing prop shaft in water

bikedaft

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mmm. could remove rope cutter and push prop further up shaft. temp fix only but would at least get me to clyde/bigger tides.

thanks for ideas :) that's what i love about this forum
 

scottie

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When was the rope cutter fitted?

If the prop is bearing against it then you will never get it to drive

Remove the collar tighten the nut solve the problem.
 

bikedaft

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only had the boat 2 years, so not sure when rope cutter added. perhaps 13 years ago when re engined. there is a spacer at g'box/propshaft flange same thickness as rope cutter so suspect an add on. not a big fan, so for the chop, probably. whether the prop will tighten on shaft depends on how much wear there is?
 

vyv_cox

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only had the boat 2 years, so not sure when rope cutter added. perhaps 13 years ago when re engined. there is a spacer at g'box/propshaft flange same thickness as rope cutter so suspect an add on. not a big fan, so for the chop, probably. whether the prop will tighten on shaft depends on how much wear there is?

I guess there's a limit but I would imagine that after tightening a 12:1 taper joint, no matter how worn, using an 18 inch spanner hard, your biggest worry would be getting the prop off afterwards. I would be rather surprised if the prop would not hold soundly.
 

Dockhead

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What you do is..... Find a piece of hose that you can clip onto your gland. Plug the other end with a plug or secure it above the water line. Jump over the side and tie something to your shaft and withdraw it enough to remove coupling inside. Jump inside and remove said coupling, secure hose over gland with shaft inside. Jump over the side and remove shaft. Simpleees!

Simpleeees way to sink your boat. Seems to me like an extraordinary risk to take, and extraordinary amount of hassle, just to save a lift or, as many have suggested, drying out somewhere.
 

colvic987

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am i mad?

need shaft off boat, prop is spinning on it. have been down 3 times to tighten it, with a 18" shifter and knee against p bracket, but still spins again fairly soon, so guess shaft or prop or both worn. no woodruff key just interference fit.

or am i being very silly? with two people should be ok ;-)

Yes, you are mad, or want to sink your boat, are you sure your prop doesnt have a keyway slot so it stops the prop spinning once tightened up on the taper, i would have thought that you can't have one without the other, so to speak. But then again i am no engineer.

I would rather be safe then sorry, get it lifted or on a harbour wall or scrubbing piles so you can check what is going on with the prop. also you can get a puller on and get the prop off.and see if it needs a keyway.
 

bikedaft

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I guess there's a limit but I would imagine that after tightening a 12:1 taper joint, no matter how worn, using an 18 inch spanner hard, your biggest worry would be getting the prop off afterwards. I would be rather surprised if the prop would not hold soundly.

well if i can get rope cutter off then that would avoid taking prop shaft out boat. for now, cos would like to get a woodruff key in there. (there is definately none at moment). and pin thru retaining nut.

of course boatyard may manage to lift her out tomorrow, but they were not hopeful until next week.
 

vyv_cox

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are you sure your prop doesnt have a keyway slot so it stops the prop spinning once tightened up on the taper, i would have thought that you can't have one without the other, so to speak. But then again i am no engineer.

I realise it isn't boat props in this case but modern machinery practice is not to use keys and keyways on anything. Keyways have been a major cause of fatigue failure in shafts on a wide variety of equipment. LNG compressor trains driven by 90 MW (yes, megawatts) gas turbines have tapered couplings without keyways. In these sizes the couplings are expanded on hydraulically but in smaller sizes (up to a few MW) often made up by bolting alone.
 

bikedaft

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but hopefully not an issue on a 1" s/s shaft with 27hp max thru it?

suspect main problem is that two nuts have loosened, allowing movement/wear of prop/shaft. so even if i take ropecutter off and tighten up prop on shaft again, the nuts may loosen again in the future, return of problem. want to fix it once and never again!
 

Tranona

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Sounds like whatever you do the shaft will be worn on the taper, so might be a good idea to replace the shaft and have it made longer to do away with the spacer on the gearbox. You can have it the correct length to give the 15mm clearance between the P bracket and the cutter (assuming it is a Stripper).
 

vyv_cox

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but hopefully not an issue on a 1" s/s shaft with 27hp max thru it?

suspect main problem is that two nuts have loosened, allowing movement/wear of prop/shaft. so even if i take ropecutter off and tighten up prop on shaft again, the nuts may loosen again in the future, return of problem. want to fix it once and never again!

No, I've never heard of fatigue failure on a yacht propshaft.

Just to clarify I'm not suggesting that retightening the prop nut, perhaps with an extra spacer, is a final fix, just to enable you to get somewhere that the job can be done fully.
 

NormanS

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Simpleeees way to sink your boat. Seems to me like an extraordinary risk to take, and extraordinary amount of hassle, just to save a lift or, as many have suggested, drying out somewhere.

Oh come on, It's only at worst a 1 inch hole, which can be plugged with a suitable wooden plug.:)

It reminds me of the time, many years ago, when I was converting an old 60 foot wooden fishing boat. She was lying in a non-tidal dock, and someone had offered to get me a new s/s prop shaft to replace the slightly worn bronze one. The boat was stripped bare, no engine etc, and there was no propeller. I set up rope blocks to handle the shaft, and had a suitable wooden plug, and a large hammer ready. Perhaps at this point I should say that the shaft was 3½" in diameter, and that I was singlehanded.

Anyway, I pulled in the shaft, which was followed by a huge rush of water. I quickly grabbed the plug, and hammered it in, phew! However, the minute I let go the plug, it shot into the boat. I finished up sitting in the water, with my foot holding the plug in. I was eventually able to shore the plug in sucessfully, but THAT was really a daft thing to do.
 

owen-cox

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Just for info I removed a shaft and changed a stern gland with a tea towel shoved in the hole to keep the water out worked perfectly and only got about half a bucket of water in after the whole job. most props are only up to a meter under water therefore only 0.1 bar of pressure behind it. easy to keep out and even if the plug falls out it takes a long time to sink a boat!.
 

savageseadog

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If you think removing the prop shaft in the water is ambitious I know someone who changed his saildrive seals in the water.

So as not to leave you you wondering I should tell you he actually did it dried down over low water.

A cautionary..........He didn't manage to complete the job before the tide came back in. As he realised that it wasn't to be finished in time, a mad panic ensued while a piece of plywood was cut sealed and screwed onto the truly massive opening.............just in time!
 
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Searush

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It is not unknown for propshafts to drop out of the back of a boat at sea when reverse is engaged for a quick stop. I have a small tapered wooden table leg taped to the side of my engine ready for just such an emergency. It will also do if a hull fitting fails or similar.
 

30boat

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It is not unknown for propshafts to drop out of the back of a boat at sea when reverse is engaged for a quick stop. I have a small tapered wooden table leg taped to the side of my engine ready for just such an emergency. It will also do if a hull fitting fails or similar.

That happened to my father's Arpege in the early eighties.He was in the cockpit wondering why the boat wasn't reversing so it was some time until he got the hole plugged.And still the boat didn't sink.
 

bikedaft

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i was talking cr @ p, when i removed the prop, there was the remains of a woodruff key. so ney key and all back in place, and boat back on clyde. stunning weather around the mull of kintyre, anchored off machrihanish beach, calm...

best buy, £50 for a mates dry suit about 10 years ago

cheers for all your replies. will get a good look at prop/shaft out of the water in next few weeks, antifoul etc

prop is very coppery. and puzzled why woodruff key broke in first place, last sudden reverse was june 2010. what is the worst thing that will happen to my de zinc ified prop if i keep using it, will it crumble/bend/disappear??
 
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