Shaft Slipped from Coupling!

Hey guys, looking for some help...

Just before the end of the day yesterday I was coming into dock put the boat into reverse and there was a clunk and then no power in either forward or reverse.
After some help getting the boat out of the water and onto its trailer and closer inspection the shaft appears to have slipped out of the coupling by about an inch although not all the way out, luckily the collar has stopped it from coming all the way out of the back and doing any damage, I don't think I hit anything solid so I don't believe there is any damage We do have serious amount of weed in the lake at the moment though.

I have not stripped everything down yet to see what has failed causing the issue but looking for any thoughts or ideas.

I'm not sure if the key is still in the shaft/coupling or if this has broken to cause the issue or even if its in the bilge but once I strip it down later I should have a better idea of whats going on.

Any advise please on things to check or what to look for.

No pictures yet but I will know more tomorrow.



Anyone know any good places for some paddles?

Let us know what you find. Only way for the shaft to come out of a correctly installed(or never messed with) coupler is for the coupler to crack, you hit something like a rock(I'm still not sure that would of done it), or a severe alignment issue(my money is on this one). But you damn for sure should of noticed the vibrations or had a trashed prop. Now if it was installed incorrectly we have 2 likely options:

1.Some idiot sanded it down to slide in instead of doing it correctly with heat(only way to do an interference fit) and hoped the key and locking screws would hold it inplace. In that case it probably just vibrated/wore itself free.

2. Otherwise I'd say the key wasn't installed at all or fell out at some point and the shaft over time spun itself loose. And even that would be a long shot in my book if the intereference fit was done correctly.

Quickest(timewise) but most expensive solution is go the ARE route. Say about $580ish and 2-4hrs. I did a big thread on option B which is very time consuming but only runs you about $85(new coupler). But I'd be hesitant depending on how bad the end of that shaft looks. If it spun a great deal you may have issues with the fit even in a new coupler.

In short Option A requires a basic set of tools and moderate automotive skills. While its the most expensive it guarantees you a good fit and that nothing is bent/worn/damaged while also being easy to install and remove whenever the mood suites you.

Option B is MUCH cheaper but requires an oven, a very good oven mit, and a pair of balls. As you'll be handling/adjusting/pushing a 500 degree 3lb chuck of metal that will instantly burn through carpet, skin, and most anything else it gets dropped on(not to mention you have about 20-30 from the oven to getting it in position before it shrinks again). If the end of the shaft is damaged at all you're playing with fire in my book, as I doubt you'd get a solid fit.

I am viewing this issue as a bit of first time owner lack of knowledge and probably something I should have found before the failure...

If I had done an alignment I would have found the issue pretty quickly, but after replacing the original prop that had a few small dings and defiantly nothing to make me worry that there was any serious damage the vibrations stopped and the prop was easy to turn with a couple of fingers so I assumed the alignment was ok and there were no issues, although it was still on my list of jobs.

The Coupling is completely shot and junk, it actually slides up and down the shaft and even has some sideways movement, I am pretty sure it was hanging on with the set screws alone, the key was probably half the length that it should be so this was almost useless. Alignment was off a little and more than it should have been but I don't know if it was responsible for the wiggle in the coupling.



Typically I had just received some new shaft packing and was going to check the alignment and repack the shaft at the same time in a week or two's time

I am now looking to source the relevant parts to get back on the water as soon as possible...

I haven't actually pulled the shaft from the boat yet to check the length although it is stamped with 54 does this sound about right?

The ARE route seems the best route to me rather than risking life and limb with a molten hot coupling onto a shaft that is probably less than perfect.

If you use the clamp on, have a keyway broached into it. A machine shop should be able to do that.

Brass castle nut?
Gore tex rope packing
Shaft seal hose.
All these item i'd rerplace them now if the actuals are of unknown age

strut bearing?

I don't have access to a propane or oxy acetylene torch but do you think a little gas canister blow torch will be able to deliver enough heat to make the prop removal easier ?
I do have an acme puller which I am using and working around a blade at a time to try and ease it off but it seems pretty stubborn and its probably a problem I will hit again so purchasing a little torch could save me a few hours now and in the future.

I don't think my prop had ever been off my 89 SN before I took it off to re-prop from original OJ to Acme. I used a propane torch to heat (they are cheap, just a small bottle of camp propane and the torch; you should be able to get the two together for less than $20. It just a few minutes; with tension on the puller and a clang, it came free. Now that they have been off, I can get them off with just the puller, no torch.

Nice tips this is why I keep coming back here as you guys keep offering the advice.
I will probably try the boiling water first as there is less chance of me loosing my eyebrows but will get a blowtorch for my growing collection of tools/parts.

Glad you got the prop off. It may have been said above, but in addition to alignment, take note of proper lapping as well. Speaking of which, I would assume the both ends of the taper need to be properly lapped?

I will be replacing mine soon, after a transmission rebuild and having the prop re-worked, so I am interested in how it goes.

I did not take note of your locations when I mentioned the cost of the propane torch in dollars; I have a friend who lives in Ashover, Derbyshire.

I'm only doing the job once so want to get it done right and will be lapping

Small world, Ashover is only 25miles from Nottingham

LOL, the UK is a small place but not that small

Say Hi to them and offer my details if they want to take up wakeboarding always looking for more crew.

Matt what strut bushing did you went for? the 2 piece ones? figure you want to allign the slot pattern between the front and back pieces.

I ordered a 1 piece 4" from go 2 marine and its works just fine. it´s even cheaper than the ones skidim offers...

bearing strut on go 2 marine

All installed and ready for the water again. (I should have cleaned up and wiped down before I took the picture)




The A.R.E sure is nice and easy to install, the alignment was a real pain but after a bit of work (2 hours sat there if I am honest) and a little heat onto one of the engine mounts everything came together and I was down to 1 thou.

New cutlass bearing installed along with new shaft packing.

My shaft packaging was well overdue replacement, this was the sorry state of what came out...4 new rings went back in



I just need to get it onto the water and check/adjust the packing.


Big thanks to all you guys for your help and assistance and the info you have put out on the site, making the entire job pretty easy.