Refitting the prop - dumb question

Stemar

Stemar

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I took the prop off to clean it up and found it was barely tight on the taper, only prevented from slipping by the key and the nut held in place by the split pin. Putting it back, when everything's nice and tight, the holes in the nut don't align with the one in the shaft.

OK, a different thickness of washer would sort it, or grinding away a bit off the bottom of the nut. but thin SS washers of a suitable size are hard to find and grinding the nut down risks a variation on a theme of the wonky table joke. Warming the prop isn't a serious option as the boat's a long way from an oven I could use and I haven't got an adequate blowlamp.

Any other ideas, or do I just have to go with one of the above? Would a plastic washer help, as it's a bit squashable?
 
Stemar said:
I took the prop off to clean it up and found it was barely tight on the taper, only prevented from slipping by the key and the nut held in place by the split pin.
Click to expand...

If it's "barely tight" on the taper, something's wrong. Might be worth lapping it in with valve-grinding paste. The taper, not the key, should be taking the drive force.
Equally, have you tried the prop without the key? You may find it's hanging up on the key, preventing it going fully home, in which case the key may need dressing down.
 
Is it not a castellated nut? You can usually turn these to the next castellation.

If it's a nut drilled with two holes at right angles then you should still be able to make a turn of less than 90 degrees. A nut with one hole is more problematic as 180 degrees is a lot of extra torque so I would use a stainless shim or two.

As said above, try it without the key and see what happens.

Richard
 
Stemar said:
I took the prop off to clean it up and found it was barely tight on the taper, only prevented from slipping by the key and the nut held in place by the split pin. Putting it back, when everything's nice and tight, the holes in the nut don't align with the one in the shaft.

OK, a different thickness of washer would sort it, or grinding away a bit off the bottom of the nut. but thin SS washers of a suitable size are hard to find and grinding the nut down risks a variation on a theme of the wonky table joke. Warming the prop isn't a serious option as the boat's a long way from an oven I could use and I haven't got an adequate blowlamp.

Any other ideas, or do I just have to go with one of the above? Would a plastic washer help, as it's a bit squashable?
Click to expand...
Sounds like its riding on the key, have you inadvertently turned it around so that a longer edge is sitting up? As others have said, take the key out, slide the prop fully home and see if it grips the taper. If it does then file the key to suit so that their is a gap between the top and the prop so it doesnt ride on it. If you have a good taper grip with out the key, mark the propshaft where the edge of the prop is and then once the key is adjusted does the nut push the prop up to your mark! If it does, tighten securely and then only think about redrilling the shaft
 
As Hekler says, Make sure its not riding on the key, if its not , my preference is to do away with the split pin and use a tab washer with one tab fitting into the key-way and three tabs bent over the flats on the nut.

Plank
 
the correct way would be to fit a new nut drilled to line up with the shaft hole when everything is done up tight.. ie; tighten the nut correctly having mark the end of the shaft with the orientation of the split pin hole. Extend this line across the face of the nut and remove before drilling. Stainless is soft and is easy to work. Don't drill the hole with the nut in place because as you break into the hole in the shaft you'll break the drill !!
 
or you step into the 21st century....have you ever tried to drill stainless.
Buy a stainless Nyloc type nut from any of the sterngear outfits, for the really careful, buy stainless tab lock washer at the same time.Torque it up exactly, no slightly to tight or too loose trying to line up that stone age split pin and you can pop on different prop with different sized boss in seconds.

https://shop.tnorrismarine.co.uk/pages/stainless-steel-propeller-shafts
 
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PlankWalker said:
As Hekler says, Make sure its not riding on the key, if its not , my preference is to do away with the split pin and use a tab washer with one tab fitting into the key-way and three tabs bent over the flats on the nut.

Plank
Click to expand...



As PlankWalker has suggested.

Easy to make out of a gert stainless washer and can be reused two or three times.
 
As 'Oldgit' and 'plankwalker' suggests. I have the same setup, using a quite thin s/s tab washer. Mine had two tabs, and one tab had to be cut narrower to fit the end of the keyway.

BTW, one is advised NOT to refit a Nyloc-type locknut after use, as the grip may be much reduced. They're cheap enough - cheaper then replacement props, so have several.
 
Aquaboy said:
The keyway doesn't always extend into the thread (it shouldn't) so you can't use a tab washer.
Click to expand...


The tab engages with the prop not the shaft, you fold the edge of the washer over a land of the nut.

Another advantage is that you can clinch it in any position and it involves no tricky drilling or lining up of holes. First time I was given one of these washers by an engineering shop, I thought: Doh! of course, this is the answer.
 
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