how to stop the prop falling off!?

Onyva

Onyva

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Have just had to CUT my very expensive Gori prop off my propshaft as neither I nor the yard could remove it the conventional way (after several attemts over several weeks).

So, I have dug out the original (still gleaming) fixed prop, that has never been used, and am planning to fit that whilst we check out OTHER folding props. BUT I can't see how the prop will stay on with just one nut ane one cone shaped anode on the end - even when they are loctited. Stupid question I know but we've had a folding prop for so long......

For those who are interested, the reason for removing the Goriprop was that Gori in Denmark refused to sell me any spares & insisted I remove it & send it back to Denmark for them to check it out - even after I told them it was impossible and that we woulmd have to cut it off if they didn't. Yes, I'm still crying! /forums/images/graemlins/frown.gif

Here's to tall ships
Here's to small ships
Here's to all the ships on the sea
But the best ships are friendships
Here's to you & me
 
Run a second nut onto the shaft so that the end of the shaft is flush with the face of the nut. Then use a good quality centre punch, put the tip on the "join" between the end of the steel prop shaft and the lock nut (looking at it from astern) and strike the punch with a hammer. Do this in 4 or 5 evenly spaced points round the junction of the nut and the shaft. It will stop the nut loosening. To get it off you will need a good socket and long bar for leverage.
 
Yes, a much more professional method certainly. I was unsure wether onyva was just wanting something temporay until he's found a new fandangled feathering prop. /forums/images/graemlins/smile.gif
 
How did you "cut it off"? Assume it is on a taper and keyway so I hope you have not cut anything off the shaft. The normal way of ensuring the prop does not come off is first to make sure that it is machined to the correct taper, slide it on the shaft until it bottoms on the taper and then put a lock nut on. Easiest way of ensure the lock nut does not come off is to use a castellated nut and drill the shaft for a locking split pin. Alternatives are to use a lock washer with one ear bent to the prop and the other to the nut, or drill and tap to take a socket headed grubscrew. You may find that you don't need a cone anode with a fixed prop if you have a hull anode close, or a shaft anode is easier to fit.
 
My prop wobbles. I tightened it when it was in the yard, took the boat out, used the engine, put the boat back on the hard, and noticed that the prop was wobbly again.
Does this mean that there's something wrong?
 
Yes. If the taper is machined correctly - both shaft and prop it should not move. Usually the difficulty is in actually shifting a prop rather than it falling off. When the prop is fully on there should still be thread showing so that the nut tightens against the prop. If the tapers are correct and the thread is too short, put additional washer(s) behind the nut.
 
I made a puller out of 25mm thick high carbon steel plates and 25mm stainless studs & nuts (like a bendix compressor) with facilities for twin & multi bladed props. "They come off with that !" Sometimes a bit heat is needed. In all cases you really need to use grinding paste to bed the new prop in. The grey marks left on shaft & prop indicate the fit and if necessary the prop needs to be spun quite a bit. When bedded on 100% it won't shift with a good key & castled nut.

That fit is all important, if the thing wobbles it will pop off in time.

www.johnhansen.co.uk

SAILING ! (there's worse things you can do with your life) <;-)
 
Ida thought that pinging out the key with a small chisel, lapping with coarse then fine grinding paste till it fits, then re-fit the key and prop with perhaps some Loctite Shaftloc or something similar would do the trick.

It should also be done up to the correct torque - which I think is usually F*****g tight.

I had the case of the shaft anode loosening - but I think that was because it was a cheap crappy anode without the steel insert to hold it in place properly.
 
If you have a keyway(spline or woodruff key) you can make a flat plate with a hole of the correct shaft and spline fit , machine or by some less technical method produce a flat spot on your cone then bend the protruding piece of flat plate so it can't slip or rotate.
sounds complicated but isn't.
 
I cannot believe I am reading this, if you dont understand the engineering theory of a tapered, keyed, fixing method then you shouldnt be trying to remove and fit props!
sorry for being so blunt but there we are. as for the others proposing all sorts of ways to do it, listen up.
A tapered shaft and prop should already be good enough to mate. make sure the tapers are clean and the key is in place and slide the prop on. put the locking washer on and then the nut, tighten up as hard as you can (assuming a 25mm shaft) with a socket and breaker bar. this will push the tapers together so that the prop taper expands and locks on to the shaft, tap the locking tab over and that is it. if you have a castellated nut then tighten it until one of the holes lines up and put the split pin in. If you have a cone anode put this on (it has nothing to do with keeping the prop on!!) and fill the hole behind the fixing screw wit some silicon to stop the screw falling out.
To take off, take off the anode, knock back the locking tab, undo the nut a few turns, and then get your 3 legged puller and put it on, tighten the puller as tight as you can and then twat the end of the puller jacking screw and the prop will jump off, it is now that you realise why we didnt take the nut off all the way, it stops the whole caboodle from falling on your toes!
The whole idea of the key and taper method is that the taper holds the bits together, the nut is just a device to make the connection and as a safety back up.
(in the olden days I used to work on diesel electric locos, the electric motor pinion which transmitted the 500 or so hp was actually a taper fit inside the shaft, it was fitted by using hydraulic pressure and then backed up with a 1" stud, the taper did all the work.
I suspect that your gori was being held on by just the taper!
Stu
 
With all due respects Stu, exactly what I said at the beginning of this thread. Interesting the two posters with a problem have not come back!

Probably a case of humble pie!
 
Well said Skipper-Stu.

The two issues I raised however, were directly related to the original post:

In probably half a dozen cases out of 100's over the past 40 years I have come across a prop that simply 'stripped' even the biggest claw puller. Probably age and over tightening in the first place caused the siezure. That is where the trusty multi studded monster I made gets the job done. Secondly I have come across a few more than a half a dozen cases where the Shaft & Prop tapers were not the same. Only maybe a thou or so out, but never the less that taper as you say 'should' do the work. If it does not the thing will probably work loose in time, even with the key and castleated split cotter fitted. A key that is loose in either keyway can also be considered unsafe. (and that happens a lot).

Another hard earned lesson I have picked up over the decades is to leave the puller on for a few hours and heat the prop core, occasionally squirting release gas on the joint. (and possibly water on the cutlass). Sometimes you walk away from it for a cup of tea and with an almighty bank the thing plops off.

As a consolation to the originator of this thread "the odd one in a hundred is an absolute swine".

Cheers

John
 
Naughty..write 500 lines..."I must not bog off when the experts are in full flow" /forums/images/graemlins/laugh.gif
 
Just got back from the boat -launched yesterday - and the prop is still on! Thanks for that Tranona, and thanks also to everyone else's too.

For the benefit of "sympathetic skipper Stu" the reason I AM messing around with props is that the YARD failed to get the prop off after several attempts over a 3 week period &, having tried everything else, suggested I cut it off - which I did very carefully with an angle grinder. My spare fixed prop fit perfectly & I used a locking washer, nut & cone anode (all blue loctited). That should do until we decide on a replacement folding prop.

Cheers & thanks for your help.
 
Ive just found this thread, which partly answers a question I wanted to put:

The boat has just been pulled out for the winter and I have noticed that the prop shaft nut is loose. It is castellated, and six months ago was wired on using thick galvanised wire, which has now corroded away.

Clearly that was the wrong method. Should I use a stainless steel cotter pin ? Or Monel, or bronze? The shaft is stainless, the prop and nut bronze.

If the tightest I can get the nut does not coincide with the single hole, should I use a longer lever, or back it off, or drill a new hole in the nut or shaft?
 
Tigten it up more!! Use a monel split pin. or 316 SS. Dont drill another hole, normally there are two holes, but you should be able to get it in line, if not remove nut, file a very wee bit off the back of the nut and refit, only do this if the holes are a small amount apart. If a long way, use a bronze washer/shim behind the nut.
 
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