Nylon bushing to reduce a prop bore?

[q240z]

I'd talk to Glide Bearings long before I used a nylon bushing. They made up a set of rudder bushings for my Roamer and can make pretty much any shape specified. http://www.glidebearings.com/Products.html

 

[saltshaker]

I run 2 1/2" bore props on 2" shafts using bronze bushings. They have been fine for over five years, props off and on a couple times when pitching them initially but no vibration or issues. Don't know that nylon would be a good choice as you are relying on the taper to transfer the torque from shaft to prop through friction, would nylon do that?
One thing to bear in mind is the prop nut needs to be bigger, a 2" nut almost fits inside a 2 1/2" bore prop, flanged nuts are made for this job. Interestingly the flanged nut of the pair is the bigger one meaning big nut first then little nut behind!

Good to hear from someone who is actually doing exactly what the OP is looking to do. Is the bushing pressed in or does it fit or have a key to hold it in place?

 

[Boatsb]

It's a cone with a slot for the key. The key is 2 sizes to fit the smaller shaft and the larger prop.
Kind of like steps.

The 16 :1 taper is maintained and the bushing compressed to make the fit. It's a pretty interesting theory but I still find it unnerving.

 

[saltshaker]

It's a cone with a slot for the key. The key is 2 sizes to fit the smaller shaft and the larger prop.
Kind of like steps.

The 16 :1 taper is maintained and the bushing compressed to make the fit. It's a pretty interesting theory but I still find it unnerving.

So the bushing goes on the shaft not fitted into the prop?

 

[Boatsb]

So the bushing goes on the shaft not fitted into the prop?

Its easier to put it on the shaft for installation but its fitted to both as it makes up the difference in the tapers.

16:1 is a standard taper and the inner and outer surfaces must match the taper of the shaft and props.

 

[Colwyn D]

Scott described my set up accurately. I initially used fine valve grinding paste to lap the bushing to the shaft and then the prop to the bushing. I had a hell of a time getting them off. I machined two 8" blind pipe flanges to fit one behind the shaft and one slotted to go over the shaft and pull on the prop hub. Four 1" studs tightened to the max and some gentle tapping until they come off with a bang.

 

[Boatsb]

Scott described my set up accurately. I initially used fine valve grinding paste to lap the bushing to the shaft and then the prop to the bushing. I had a hell of a time getting them off. I machined two 8" blind pipe flanges to fit one behind the shaft and one slotted to go over the shaft and pull on the prop hub. Four 1" studs tightened to the max and some gentle tapping until they come off with a bang.

So why not get the right size props?

 

[SeaEric]

So why not get the right size props?

I can answer that one: My friend was quoted $22,500. for a new set of the exact size match.

 

[Boatsb]

No one said boating was cheap.

A buddy put $35K into CNC wheels for his 52. Got an extra 1.5 Kts. Smooth performance and increased efficiency.

 

[34Hatt]

you would still have the key in the key way and the prop nuts that would contact metal to metal so electrolysis should not be a problem, that said he should just get the right props........Pat

Don't forget about the Nut that it jammed against the hub and is in contact with the shaft!

They have been using these for at least 15 years that I know of/

And yes small nut first followed by the Large nut

 

[Boatsb]

Don't forget about the Nut that it jammed against the hub and is in contact with the shaft!

They have been using these for at least 15 years that I know of/

And yes small nut first followed by the Large nut

Stop before this gets nuts.

 

[saltshaker]

I can answer that one: My friend was quoted $22,500. for a new set of the exact size match.

Plus the cost of the shaft and labor. Amazing how fast this stuff adds up. He should seriously consider contacting his insurer. This isn't a small claim.

 

[Colwyn D]

So why not get the right size props?

I bought a used pair of Michigan wheels 'as new, 2" bore' from a guy up north, I'm in Florida, paid $1500. Spoke a fair bit on the phone and sent plenty of photos but when delivered found out they were 2 1/2" bore. I was out the country when they were delivered and the yard manager signed for them. Seller said tough luck they're yours now and I hope his boat has sunk!
Entirely happy that I found the reducers and not really a down side, maybe an in water prop change and you drop one but nothing else. Suppose also if I went looking for props again I have the option of two bore sizes. I keep the worn original 2" set as spares on board.

 

[SeaEric]

Plus the cost of the shaft and labor. Amazing how fast this stuff adds up. He should seriously consider contacting his insurer. This isn't a small claim.

He did. They're involved for the one shaft and prop. Upon investigation, the other shaft has a crack too. He will be replacing that one on his dime.

 

[John F.]

Fwiw, I got the bronze ones. The prop/shaft guy said that the commercial crabbers, who are shifting into and out of gear all the time at their pots, will only use the bronze. The nylon don't hold up to that. The reason I'm using them is that the PO bought a set of nice 4-blades that are 1/8" to big. Same thing as above. When he got them, they weren't the right size but he kept them.