Can’t get new prop onto shaft

[sailah]

See if the prop manufacturer would send you a bare hub with a deposit that way you can check before disassembling. As a manufacturer, I'd do that for a customer that just spent 1000s. Probably without a deposit honestly.

If not, I'd take it apart. It went together with human hands and it can do it twice. Far more appealing than any of the other options in my eyes.

[ithet]

Originally Posted by OrangeCrush

He said that the way to go is to cut some of the tapered threading off the shaft. He said that’s what they do with MaxProp which is similar.

But you would not need to do that for a MaxProp, for which you first fit the hub, then the blades and case are then assembled around in situ.

Seems like you need to do similar.

[OrangeCrush]

Originally Posted by ithet

But you would not need to do that for a MaxProp, for which you first fit the hub, then the blades and case are then assembled around in situ.

Seems like you need to do similar.

Makes sense, but the Variprop is not meant to be disassembled by the user. Its inner workings are a bit more complex than the Maxprop, but I'm sure still not impossible. Even without the blades, though, it may not fit without some of the other measures. The idea of borrowing a hub to check it first is a good one, sailah.

[DougR]

- Take the existing zinc off of the shaft.....you don’t need it anymore because the prop has its own zinc....then shorten the front of the shaft by slightly less than the thickness of the old zinc and slide the shaft forward. Trim the cotter pin nub off the back of the shaft and maybe a thread or two as well. That will probably get you what you need.

- Is there a flex coupling between the gearbox and the prop shaft coupling??

[hpeer]

Originally Posted by DougR

- Take the existing zinc off of the shaft.....you don’t need it anymore because the prop has its own zinc....then shorten the front of the shaft by slightly less than the thickness of the old zinc and slide the shaft forward. Trim the cotter pin nub off the back of the shaft and maybe a thread or two as well. That will probably get you what you need.

- Is there a flex coupling between the gearbox and the prop shaft coupling??

I’m no pro, but this makes more sense to me.

I like to think about the next thing to fail, what do I do if?

If at all possible I would want a solution where the prop could be removed in the water.

In any case whatever you do I would suggest removing the shaft and inspecting it. Sounds like you are going to a lot of work and it would suck to find you need a new shaft in 2 years.

But also a shaft is likely a lot less expensive than that prop.

As to the zinc, I’ve never been able to keep a zinc on my shaft. Always throws it. So I painted my prop with an Petit RustLock primer. It’s a little bit of urethane paint with a lot of aluminum dust. It works like a zinc, not as well but better than nothing. My surveyor says he knows others who have done the same thing for years.

[a64pilot]

If you cut off the cotter pin hole, (I did) then drill the two nuts used on the old prop for safety wire, that way if you need to you can put the old prop back on and secure it.
A feathering prop weighs more than a fixed prop, so you want to get that heavy prop as close to the Cutless bearing as you reasonably can, so shorten the shaft to prevent whirl.

Whatever solution you come up with you certainly want to be able to pull the prop and put your spare on with the boat in the water if you ever cruise anywhere.

[skipper53]

Really entry saw a video of having to cut the shaft and use dye on the hub. Check You tube on sailing Project Atticus, or Bums on a Boat.
One of them just went through this very same thing. Good luck!

[OrangeCrush]

Great advice, all. This is very helpful.

I agree that I can easily lose the shaft zinc which buys me at least an inch, but I think there may also be a minimum amount of "overhang" (exposed shaft) required behind the stern gear for some reason(?). It hadn't occurred to me that it would be good to get it closer to the cutlass bearing because of weight, but yes the new prop is quite heavy.

The shaft is only a year old, it was replaced along with all my stern gear when I had a hole in the old shaft log on the way to Bermuda. I had the work done at a yard so I haven't taken the coupling apart myself to understand how it actually works. It's not flexible, just a standard coupling with what looks like a bolt for a set screw. Not corroded and pretty accessible.

If I temporarily remove the coupling to slide the shaft forward a bit, plus the removal of the cotter pin nub, I may not have to cut the front of the shaft. Or, I could cut the front of the shaft and maybe not need to cut off the cotter pin nub. 2 out of 3 might be good if I'm lucky. If it comes down to a choice between the two, it seems like cutting off the nub is a lot easier than trying to trim the front of the shaft.

If I shortened the front of the shaft, wouldn't I have to be careful to make a perfectly square cut? And does that set-screw bolt match up with a hole in the shaft or is it just pressing against it from the outside? I guess I would cut it in place with a hacksaw, being careful not to torque the packing gland, or I could slide it out completely but then I would have to repack the stuffing gland afterwards. It seems like cutting off the nub would be a lot less tricky, but I'm a bit ignorant on the coupling itself so if anyone can tell me what to expect on with that it would be much appreciated.

[Wotname]

Originally Posted by OrangeCrush

.............

If I shortened the front of the shaft, wouldn't I have to be careful to make a perfectly square cut? And does that set-screw bolt match up with a hole in the shaft or is it just pressing against it from the outside? I guess I would cut it in place with a hacksaw, being careful not to torque the packing gland, or I could slide it out completely but then I would have to repack the stuffing gland afterwards. It seems like cutting off the nub would be a lot less tricky, but I'm a bit ignorant on the coupling itself so if anyone can tell me what to expect on with that it would be much appreciated.

The answers to these questions depends on exactly what style of coupler you have. A picture may help.

As a generalisation, you don't have to cut perfectly square and the the set screw often rests directly against the shaft although some do dimple the shaft where the set screw engages the shaft.

However it is in the detail of how your coupling is set up and we don't have that detail.

[OrangeCrush]

Originally Posted by skipper53

Really entry saw a video of having to cut the shaft and use dye on the hub. Check You tube on sailing Project Atticus, or Bums on a Boat.
One of them just went through this very same thing. Good luck!

I just found the one where they remove the shaft and cutlass bearing, then the next episode where they reinstall everything. Didn't see them cut the shaft or use any dye (maybe a later episode?) but it's still helpful to watch them work on the coupling.

I suppose I could also take this opportunity to cut the shaft down even more and install a flexible coupling.

[OrangeCrush]

Originally Posted by gonesail

beautiful looking prop by the way. hope you get it on without too much trouble

Thanks! Can't wait to see how it works.

[OrangeCrush]

Hey folks,

It was an ordeal but I finally got the coupling off and took the shaft out. My intention is to cut 5/8” off the front of the shaft (and shorten the key) to bring the overhang down to the desired 1” (between cutlass bearing and start of taper).Then I’ll cut off the little cotter pin nub, and that should give me what I need to get the new prop on.

My main concern is how I’m going to get the shaft back into the coupling after I trim it. There was a ton of friction getting it off and it won’t go back on now. It probably would if I heated it and pounded it, but I can’t do that without damaging the coupling. Can I sand down the shaft/coupling surfaces so that it slides in?

Or would I be better off getting a new shaft made that’s shorter? (My shaft is only a year old so I’d rather not)

Any further advice is greatly appreciated as always!

[Wotname]

One possibility you could try is to cool the shaft with say ice packs and heat the coupler in an oven to say 200 to 300 (F) and it might slide with no more than a gentle tap.

You will need decent gloves of course .

At least this is easy to try while the shaft is out.

[Sailmonkey]

You’ll need a new coupling, and have it fit/faced to the shaft.

The coupling is fit with minimal clearance when originally machined, after fitting a little corrosion more or less locks them together. Pulling them apart changes the fit.