Question about split coupling

[cdhickey]

I'm currently in the middle of a monster job that started as a simple cutlass bearing replacement and has led to me deciding to replace my prop shaft, coupling, stuffing box and propeller. The full story (and all the gory pictures) will follow in a separate post!

Given the trouble with removing the previous coupling (it never did come out- I cut the shaft after much frustration) I decided to go with the Moyer split coupling. It arrived in the mail today, but I was surprised to find that it seems to be a much, much tighter fit than I had expected. I've got a new shaft on the way, but I tried a test fit with the old one and I could not get the shaft to fit in the coupling even without any of the bolts installed. I didn't force it too much because I didn't want to cause any damage, but I'm definitely concerned now about how this is going to work.

Before I break or ruin something (else!), has anyone tried installing one of these before? Should the fit be this tight, or am I doing something wrong?

[Mo]

Chris,

If you are having things get out of hand there go talk to the boys here. Jeff Davis ownes it. He's from my old stomp'in grounds and he's married to my cousin (a Mullaley)...and to top it off their daughter is on the Canadian Womens National Hockey Team Jeff is a good man and although he deals with propulsion on large ships I'm sure he'd know exactly what you need etc or would put you onto someone. Worth a call.

Atlantic Propeller Repair Limited
12 Kyle Ave
Mount Pearl, NL A1N 4R5, Canada - View Map
Phone: (709) 747-9200

[cdhickey]

Thanks, Mo! That may come in handy.

I think I've got the project under control for now, it just turned into much more than planned as I dug into it. In checking out the cutlass bearing I noticed some damage and scoring on the shaft, and the stuffing box hose was looking like a disaster waiting to happen. I figured I might as well do it right the first time around for a change!

[CalebD]

Chris,

Your experience of wanting only to replace the cutless bearing leading to the whole job sounds just like how it went for me as well. It boils down to the old "while you are there..." routine.
I can say that we were able to re-use our original coupling and stuffing box though. You might be amazed at how nicely a well made bronze stuffing box cleans up with a wire brush on a work bench.

http://www.odalisque.us/2011/12/2011-november-30th-begin-drive-train-rebuild/

Good luck with your drive train rebuild.

Caleb d.
Tartan 27' #328

[hanleyclifford]

I'm currently in the middle of a monster job that started as a simple cutlass bearing replacement and has led to me deciding to replace my prop shaft, coupling, stuffing box and propeller. The full story (and all the gory pictures) will follow in a separate post!

Given the trouble with removing the previous coupling (it never did come out- I cut the shaft after much frustration) I decided to go with the Moyer split coupling. It arrived in the mail today, but I was surprised to find that it seems to be a much, much tighter fit than I had expected. I've got a new shaft on the way, but I tried a test fit with the old one and I could not get the shaft to fit in the coupling even without any of the bolts installed. I didn't force it too much because I didn't want to cause any damage, but I'm definitely concerned now about how this is going to work.

Before I break or ruin something (else!), has anyone tried installing one of these before? Should the fit be this tight, or am I doing something wrong?

Since you cut the shaft and did not get the old coupling off I'm thinking you tried the new split coupling on one of the cut pieces. Not sure what you cut with but it is likely not a clean cut with a beveled or rounded edge. The tolerance on these things is less than .001" and there can be no burrs or boogers whatsoever. Wait for the new shaft and test it first without the key after wiping light machine oil on both pieces.That will give you a better feel for how it is supposed to fit.

[Mo]

Thanks, Mo! That may come in handy.

I think I've got the project under control for now, it just turned into much more than planned as I dug into it. In checking out the cutlass bearing I noticed some damage and scoring on the shaft, and the stuffing box hose was looking like a disaster waiting to happen. I figured I might as well do it right the first time around for a change!

Oh yes, for sure, when tackling something like that do the whole thing and you know what is there. Good to see.

[cdhickey]

@hanleyclifford- good point. The shaft looks fairly clean, but it is quite possible that it is not quite clean enough. I'll re-try the fit when I've got the new shaft in hand.

@CalebD- yes, very similar, and I actually looked at your pages as I worked through it! I think I'll be able to salvage the stuffing box itself, but the hose and clamps are being condemned.

@Mo- I plan to have this boat a long time, so my motto is do it right and let the kids worry about it next time!

[hanleyclifford]

Another Suggestion

Take your new split coupling into the house and let it warm until the shaft arrives. The miniscule expansion might be just enough to make the fit.

[Al Schober]

Chris,
You should be able to measure the two pieces and figure out what's going on - and I mean with something better than a tape measure. Your tool set should include something capable of measuring to .001". I started out with a vernier micrometer years ago, but that would only do outside and was only good to 1". I then bought a dial caliper that went to 6" or so, but it was a cheap plastic thing and never seemed to come back to zero when closed - but it would measure IDs. Moved up in dial calipers and spent the big bucks for a Mitotoyo - nice tool but I'm nervous every time I take it out of it's case. Latest is a digital unit from Harbor Freight that I'm quite happy with. Cheap enough to beat on, but seems accurate and repeatable. Highly recommended.
As for your split coupling, I wish you luck - I've never used one. I've worked on numerous shaft couplings, all solid, ranging from the 1" slip-on for my Atomic 4 up to a few over 26" ID that had to be heated to fit onto (and off) a tapered shaft. If they don't fit, figure out why before fixing the problem - it's a bummer to modify the wrong piece. With the A4, the problem is usually corrosion of the inside of the iron coupling. Clean up the coupling (7/8" dowel and sandpaper) and it goes on easy.

[cdhickey]

As an update: you guys were right, as always.

My shiny, brand-new shaft arrived and was a perfect tight slip fit with the split coupling. I had to file the key ever so slightly to clean up a few little burrs, but it looks like this is going to work very nicely.

My plan is to install this week- I'll try to put up a few pics for future reference.