Prop shaft key - how tight should it be? Should I use anything to hold it in?

MikeCalypso

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I'm changing my prop and the key on the shaft came off really quite easily with a pair of pliers and a light pull. I guess I can be happy about that having seen many people have a horrible struggle.

There is a bit of white stuff in the key hole which looks like it could be some old adhesive or grease or maybe just corrosion/salt deposits. Now I've cleaned these up the key can push in quite easily with a firm pres with my fingers. Is that enough to hold it in? Should I be applying anything else in there to either hold it in or help it come out in the future or should it just go in bare?

I'm worried if it's not tight enough it may move slightly in the small gap that is required by my prop manufacturer to be between the prop and the key.
 

scottie

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I'm changing my prop and the key on the shaft came off really quite easily with a pair of pliers and a light pull. I guess I can be happy about that having seen many people have a horrible struggle.

There is a bit of white stuff in the key hole which looks like it could be some old adhesive or grease or maybe just corrosion/salt deposits. Now I've cleaned these up the key can push in quite easily with a firm pres with my fingers. Is that enough to hold it in? Should I be applying anything else in there to either hold it in or help it come out in the future or should it just go in bare?

I'm worried if it's not tight enough it may move slightly in the small gap that is required by my prop manufacturer to be between the prop and the key.
Sounds like it’s been properly fitted
Tidy up and replace dry
Try a little brass o polish to give a very fine lap in but only really as a cleaner
And think kindly of the tradesman who fitted it as the others you refer to were bodgers
 

rotrax

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The key is purely a locator. The drive is taken by the taper. Very important to ensure the prop/shaft joint is not 'keybound'.

This means putting the prop on the shaft without the key, pressing home fully.Mark the shaft at the furthest forward part with a turn of tape.

Now remove the prop-might need a clout-and refit with the key. If it does not reach the turn of tape, the key will have slipped and jammed, stopping any further rearward progress.

As a motorcycle dealer for many years I dealt with many damaged/worn taper fits. Centre punching the sides of the key can be a good way to hold one in place, as is sticky grease.

The bottom line though, is ensuring the key does not restrict the fit.
 

Graham_Wright

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Um!
"The key is purely a locator. The drive is taken by the taper. Very important to ensure the prop/shaft joint is not 'keybound'."
That's what I thought! I slid on my prop by hand and didn't apply the nut. It declined to "slide off" again and I needed a puller.
Full of confidence, I refitted and tightened up the nut.
First time out,the prop came loose.
It happened again and then I machined a keyway and fitted a key.
No further problems.
 
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