Prop Shaft keys HELP!

[Kens]

After loosing drive at the entrance to Portsmouth Harbour on Bank Holiday Monday afternoon, ( Sails back up, pick up a mooring bouy and call for a tow, all done smoothly and without panic, well not that you could see anyway, with just about every boat in creation coming up behind us!), we found, after throwing the skipper over the side with a mask and a torch, that the prop shaft key had sheared, and we can't find any info regarding this insignificant looking little piece of metal. So the questions are:-
Is this a common occurrence?
Is the material important?
What pitfalls are we looking at when putting it all back together again (Hopefully without lifting out!)
WHERE DL DO WE GET ONE FROM ??
The name of a siutable supplier in the Gosport area would be good too.

Thanks in advance.

Ken.

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[paulrossall]

I would grease it so it fits easily and helps to prevent any corrosion. You will get them from any boatbuilding yard or from a propellor supplier.

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[dickh]

Should not have sheared under normal circumstances, the taper must be a good fit(requiring a puller and a sharp hammer tap to release) and the nut should be tight with a split pin. The material in mine looks like Brass or Bronze, certainly not stainless. Get from local propellor supplier or marine engineer, make sure it's a snug fit in the groove, grease well on assembly and away you go!
You can do it whilst dried out against a quay or piles to save the cost of lifting out, but make sure you have all the right tools to hand + an engineer nearby just in case there are other problems you uncover!

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I'd rather be sailing... /forums/images/icons/smile.gif

 

[Johnjo]

Before fitting the new key would suggest refitting the propeller without a key, tightening the nut,
then marking the shaft where the prop reaches, This is where the prop should fit when the new key is fitted, remove the propeller fit the new key and retighten, If the prop
does not reach the mark you made on the shaft the key is standing proud and will need filing down until a snug fit is achieved.

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[Ivy]

To get the right thickness of key take the prop in to the suppliers. If you have a stainless steel shaft then I would think a stainless steel key would be best, bronze is a bit soft and you might get the same problem.

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[Heckler]

when i was an apprentice the first thing we had to do was make keys, stock oversize keys were kept in the stores and we had to file them down by hand, we were always taught that a tapered shaft drive used the taper to do the driving and the key was only part of the equation. as dick says, make sure the taper on both parts are in good condition, make marks to make sure that the finished tightened product goes to where it should, you should be able to measure the "square" when the prop is on without the nut if the keyway comes to the end of the taper, if it is a rounded rectangle in the shaft , measure length, width and depth of the slot and measure the depth in the prop slot add the two depths together to get the thickness of key needed.
go to the local chandlery or boat yard and ask them for some key stock, approx the size you need in stainless and then comes the fun bit as you file it to fit, nice and snug mind!!
grease and tighten up and make sure that it goes to where it should on the shaft, if it doesnt the key is too fat and needs some more taking off,
best of luck and if any one wants to natter about fitting gears to shafts with gib head keys? or fitting slider block cheeks in locos by scraping with an engineers scraper?
stu

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