Nylon bushing to reduce a prop bore?

[SeaEric]

My friend who's looking for a pair of props (see post in the parts wanted forum) has found a pair that may work but the bore is 2 1/2 instead of what he needs which is 2". The prop guy says he can add a nylon bushing to reduce the bore to 2". Has anyone had experience with this? Does it work ok? Is a nylon bushing robust enough to endure?

 

[Boatsb]

My friend who's looking for a pair of props (see post in the parts wanted forum) has found a pair that may work but the bore is 2 1/2 instead of what he needs which is 2". The prop guy says he can add a nylon bushing to reduce the bore to 2". Has anyone had experience with this? Does it work ok? Is a nylon bushing robust enough to endure?

I'm kind of conservative on things like that. I'm not a fan of bushings in general on props but if it's a boat that idles up and down the ditch duct tape may work for him.

 

[John F.]

They make nylon and bronze. I was just at Kastel Bros looking into this. Barney said that they work fine, and that the nylon is ok for awhile, but that the bronze is better long term. if your friend is local to St Mike's, check with Kastel. They had a bunch of different sizes. I'm trying nylon for this season, and if I like this set of wheels, will replace with bronze next winter

 

[Boatsb]

They make nylon and bronze. I was just at Kastel Bros looking into this. Barney said that they work fine, and that the nylon is ok for awhile, but that the bronze is better long term. if your friend is local to St Mike's, check with Kastel. They had a bunch of different sizes. I'm trying nylon for this season, and if I like this set of wheels, will replace with bronze next winter

Why would you try the nylon if you know the bronze is better?

I'd look for the right size props myself but to each his own.

 

[saltshaker]

Most use the bronze bushings. Never heard of anyone having a problem but it wouldn't be my first choice by a long shot. His options may be limited as those are pretty big props for 2" bore. I'd want a matched set unless I found an exact replacement for the one prop.

 

[Avenger]

Nylon is hygroscopic, meaning it absorbs water and swells (I'm sure Bob is going to correct me here, so sorry if I fouled up the details). Maybe that will resist the tendency of plastics to cold form, but I'd be a lot more comfortable with a bronze adapter that isn't going to change shape. It doesn't take much to screw up a shaft when there's a big mass spinning at high speed on the end of it.

 

[SeaEric]

The reason he needs the prop is that he rung off a shaft and lost the prop. I agree that the 2" is marginal but that's what Hatt put in her. Its the last 39C built, 1998 and the only one with Cummins 450's from the factory. I'll mention the bronze sleeves to him. The boat is in Fl, currently disabled on the West Coast. I know Kastel Bros. I'm right up the road from them.

 

[saltshaker]

The reason he needs the prop is that he rung off a shaft and lost the prop. I agree that the 2" is marginal but that's what Hatt put in her. Its the last 39C built, 1998 and the only one with Cummins 450's from the factory. I'll mention the bronze sleeves to him. The boat is in Fl, currently disabled on the West Coast. I know Kastel Bros. I'm right up the road from them.

If he has an insurance claim they should replace with a new set not just one. 2" bore is fine but you don't typically find props that big running on 2" shafts. That's a big shaft and wheel for 450Cs. Must have real deep gears. Never find a setup like that on an Ocean.

 

[SeaEric]

New is 2 months out special order. He'd like to have her back in service sooner.

 

[jim rosenthal]

I'd use bronze. Isn't nylon going to insulate the prop from the shaft- which you don't want? It won't insulate it completely, but I still don't think it would be good. And I would think bronze will hold its shape longer and get out of balance less.

 

[saltshaker]

I'd use bronze. Isn't nylon going to insulate the prop from the shaft- which you don't want? It won't insulate it completely, but I still don't think it would be good. And I would think bronze will hold its shape longer and get out of balance less.

Interesting point. If the prop is insulated from the shaft how do you provide electrolytic protection?

 

[luckydave215]

Nylon is a terrible material for that application. Under load it flows plastically forever, it won't stay tight. Try clamping a Nylon washer under a bolt and see what happens.
In addition you can expect it to grow 20% in size as it goes from fully dry to fully saturated with water, so if it experiences a wet/dry cycle (haul out) it will be sloppy loose.

 

[Fanfare]

Did this boat have the Hatteras muff couplings? My understanding is that the muff is designed to work like a shear pin and yield first when you hit something. Then you only have to replace the stub shaft and/or prop instead of the entire shaft and maybe damaging the transmission. I have never found anybody with this experience. It seems to me that hauling these muff couplings around just ahead of the props is very disturbing to the flow of water. A one-piece shaft should help. But Jack Hargrave and Hatteras put these muffs on for a reason; both are well above my pay grade. I need more info!

 

[doc g]

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

 

[jim rosenthal]

With a nylon bushing, you would still have some metal-to-metal contact, but it would be over a smaller area, which I don't think is what you want. And nylon, if it continues to flow, and swell underwater, wouldn't last very long before its shape changed and then the prop wouldn't be on center, would it? I think bronze is better.

 

[saltshaker]

Did this boat have the Hatteras muff couplings? My understanding is that the muff is designed to work like a shear pin and yield first when you hit something. Then you only have to replace the stub shaft and/or prop instead of the entire shaft and maybe damaging the transmission. I have never found anybody with this experience. It seems to me that hauling these muff couplings around just ahead of the props is very disturbing to the flow of water. A one-piece shaft should help. But Jack Hargrave and Hatteras put these muffs on for a reason; both are well above my pay grade. I need more info!

Hatteras stopped using 2 piece shafts long before this boat was made. Two piece shafts are a good idea in theory but they introduce more problems then they are worth. I replaced the 2 piece shafts on my 46C. One of the best upgrades I made to the boat.

 

[Boatsb]

Hatteras stopped using 2 piece shafts long before this boat was made. Two piece shafts are a good idea in theory but they introduce more problems then they are worth. I replaced the 2 piece shafts on my 46C. One of the best upgrades I made to the boat.

I think 2 piece shafts are still popular with the crawler crowd. If you hit something at 5 kts and bend the shaft end the replacement is easier. They also see no need for the improved performance of the single piece shaft.

 

[Walter P]

Jack, How did your 46's performance change after you installed the one piece shafts. Also didn't you replace the engines at the same time..... if so, how were you able to tell that their was a shaft advantage.... I know your 46 was was a good performer and am curious. I have the muff couplings on my '82 series I 48 MY and I was wondering if there would be any noticeable advantage in my case to one piece shafts.

Walt

 

[saltshaker]

Jack, How did your 46's performance change after you installed the one piece shafts. Also didn't you replace the engines at the same time..... if so, how were you able to tell that their was a shaft advantage.... I know your 46 was was a good performer and am curious. I have the muff couplings on my '82 series I 48 MY and I was wondering if there would be any noticeable advantage in my case to one piece shafts.

Walt

I had 8V71Ns so the boat was very slow to begin with. I had some vibration I couldn't get rid of so I replaced the shafts. I gained almost 1.5kts top end but the big difference was how smooth the boat ran. I repowered a year later so I had the new shafts for a full season before the engine swap. Only other comp I had was another 46C that was repowered with the same engines and similar gear ratio. He had the old two piece shafts and ran about the same as me. Big difference was I had 2" less pitch and was underpropped while he reworked his props and was running on spec. I probably would have picked up another 1.5-2 kts had I repitched the props. My boat maxed out at 2400rpm with a full load. Top end was pretty much the same regardless of load.

 

[Colwyn D]

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!