Key Material for Bronze Prop

[fstbttms]

Originally Posted by SkiprJohn

Aloha Wheels,
Thanks. That clears up why that nut has a threaded hole in the end of it. Unfortunately there is no corresponding threaded hole in the end of my shaft. I suppose I could tap one. Might be hard since I've reinstalled the shaft again.

It is unlikely that this would be a viable solution in any case. All feathering props that I have installed require that, at most, only one shaft thread be visible beyond the after end of the nut because any more than that interferes with the operation of the blades. It is common to have to actually cut excess threaded shaft end off when installing these props. There probably would be no room for any kind of screw to extend from the end of the shaft.

[fstbttms]

Originally Posted by SkiprJohn

fstbttms,
I suppose then I should use a stainless key instead of bronze.
JohnL

If it gives you piece of mind, why not? But I think that bronze keys are fine and probably 99% of all boats that use shaft keys live out their entire lives using bronze keys with no problems. And again, I suspect a failed key would most likely be due to owner neglect (ie: unchecked corrosion), presumably not an issue here.

[SkiprJohn]

In your opinion, is any kind of play between key and sides of keyway acceptable or should it fit extremely tight?
JohnL

[fstbttms]

Originally Posted by SkiprJohn

In your opinion, is any kind of play between key and sides of keyway acceptable or should it fit extremely tight?
JohnL

I say it should be a snug enough fit that the key doesn't drop out of the keyway when you rotate the shaft upside down. But not so tight that you can't fit it into the keyway easily by hand. "Finger tight", if that can be applied here.

[delmarrey]

If a key shears, then the locking taper fit is not tight enough. The key is there for back up, not to do the driving.

What tool is used to tighten the nut? mine has a 1/2" square hole for a socket extention. And to hold the nut in place cotter keys go thru the side of the prop and into the sq. hole, where it is spread apart.



http://www.martec-props.com/Green/install_eliptec.gif

[fstbttms]

Delmarrey, the pic of the Martec folder reminds me that I installed one just last week. It replaced one that had lost both blades because the "ears" that house the pivot pin had both broken clean off. That's a new one on me, never seen it happen before.

[Alan Wheeler]

John your on the right track. Drill and tap the end of the shaft to take a set screw. I think that is what you would call them over your way. You won't need to take the shaft out as long as you drill reasonably straight.
fstbttms, the shaft in question does not stick out. It is the threaded socket at the end of the prop that has the hole in it, and the shaft has a threaded hole that a set screw screws into to lock that backing nut on.
Normal practice for a key is a snug fit, Just as fstbttms suggested.

[delmarrey]

Originally Posted by fstbttms

That's a new one on me, never seen it happen before.

Yeah! Me too! someone must have used the wrong material or cut the grove too deep. My pivot pin is Inconel. The wear shoulders on my blades are about worn out. So I'll be replaceing it this winter with the geared blades unit

[SkiprJohn]

This from Senor Mechanico

Gori instruction sheet
Here are a couple of photos of my Gori instruction sheet.
I hope they're clear enough.
Steve B.
Attached Thumbnails