loosing shaft out of coupler

[Hiker_00]

It's creeping aft on its own and it's not good.

Launched last friday and now I think it will have to be pulled again. I installed a new MM Split Coupling this spring. It seemed to reassemble securely but it's halfway out and can't take much more.

So any thoughts about this coupling and maybe ideas what I did wrong?

Thanks in advance.

Tim

[hanleyclifford]

This happened to me once. Try to pull the shaft back to it's correct position. Remove the setscrews to be sure you are dead on the provided depressions and try to tighten again. Mark the shaft with a magic marker and watch it closely for a few weeks.

[jhwelch]

If there is any danger of the shaft getting free put a zinc donut on the shaft on the inside to act as an emergency stopper.

[Mo]

If there is any danger of the shaft getting free put a zinc donut on the shaft on the inside to act as an emergency stopper.

That's a good idea if there is room. Never really thought of it before but I guess that might keep it out of Davy Jone's Locker.

[lat 64]

If there is any danger of the shaft getting free put a zinc donut on the shaft on the inside to act as an emergency stopper.

Brilliant! I even gave it a vote too

[tenders]

That's a good idea if there is room. Never really thought of it before but I guess that might keep it out of Davy Jone's Locker.

I do that on my boat not because I think the shaft will depart the boat - it probably won't - but because I don't want it ripping through my rudder at 2000 rpm as it attempts to.

[Dave Neptune]

Collar it!!!

I was with a friend when he learned the hard way. He had just replaced the shaft housings and I straightened the shafts for him. When done we were launched from Cabrillo Boat Works in the LA Harbor. The boat was a 32' Chris woody with a fly bridge and a pair of Chevy 350's. We got her lit and across the harbor we started to test and head for Long Beach. The boat was running flawlessly and the shafts were very smooth. We settled in at around 3400 RPM's and cracked open a couple of beers to clelbrate when a lil boat cut across our bow abruptly, Bill trrottled back to the stops and a collision was avoided! However when he backed off we heard some horendous (the hatches were open) noises from the rear of the boat and water was running in fast through two holes, one from the empty shaft log 1 1/4" and the entire rudder through hull supports. When he throttled back the port shaft came loose and the spinning prop destroyed the rudder post et all. I got thigs plugged under water and he pluggved the log. Then we headed back to the yard as the cradle was still ready. Never found the shaft or prop and he had a very big bill when all was back in order.
Since then I have always commented when I see no retaining collar on a prop shaft!!!

Dave Neptune4

[Hiker_00]

I've put two zinc collars on the shaft so there's little chance it will fall out and be lost. That's good news.

Now what to do? It's clear there'll be a $400 charge to take a travel lift ride to and fro. I'm wondering if this can be fixed in the water. The install took pounding (lightly but firmly) to seat the shaft in the split coupling. The whole coupling is not split. The last part is compression.

There's frighteningly little room between packing gland and coupler. It's like an inch or maybe two. The push has to come from the prop. All the packing has to come out to then spin the gland nut back down to increase the room to allow the key to placed in the shaft.

I also don't know what went wrong. The shaft did not spin in the coupling. The key is in the slot. I guess the set screws clamping the whole thing tightly are not doing the job. There's only so much torque one can exert with a allen wrench.

Any ideas?

Tim

[Dave Neptune]

Worth a try?$?

Tim, can't help much regarding the flange. However if you have room as I did in my boat, I shortened the hose on the box.
I also did an R&R to straighten the shaft and replace the entire stuffing box while in the water. I used a stub of plastic rod to pack the packing while working on the shaft. When I was ready to have the diver slide in the straightened shaft I slid off the old stuffing box and kept water to a minimum with a hand towel while he slid the shaft in gently and I held the new box in place. I was ready and had less than a gallon of water ingress in the two removals ie the shaft and then the box to slide in the new. Once the parts were in place and not adjusted or fastend yet there was just a bit of dripping I would hardly call a stream ~ no worries.
I have done many shafts in this manner when I was doing a lot of straightening for hot boat and sailboat projects I was involved in.

Dave Neptune

[tenders]

A diver with a sledge could tap the shaft in from the water and might even have a little slide tool to make the job easier. I would definitely give this a try in an effort to save $400.

Something to consider, though, is the hole drilled in the end of the shaft for the cotter pin. It is possible to beat too hard on the end of the shaft and bend the little bit of metal between the aft end of that hole and the aft end of the prop.

[Hiker_00]

Thanks Dave and Tenders and others...

The shaft alignment was a challenge on land. The shorter MM key and my shaft are not matched. It all works but getting everything to slide in as one was hard. It took a bunch of attempts. Doing this with a sledge while underwater in 50deg cold sounds tough.

I've reached out to Don M and to my truck hauler. I've proposed sitting on his trailer for an hour to do all this work. un pack gland, pull shaft, re seat key and install shaft, tighten, re pack gland. I don't know if he'll like it.

I also do not know why I failed on the first attempt. Hopefully Don has some thoughs. Also, there are no through set screws to match up to a dimple in the shaft on these couplers. It's just the 4 screws on the side to clamp it down and key to hold in place.

Tim

[romantic comedy]

It is hard for me to picture your situation. I juat want to say that taking out a shaft in the water is very easy. Well, as easy as it is on land.
If the shaft would usually just slide out with no interference, then the same will be true underwater.

Like the other response, I have done this on a few boats. With my A 4, i have a 1 inch shaft. I just have a diver pull the shaft, and I follow it with a 1 inch dowel, with a little tape to make a taper, so it does not disappear.

I have been the diver, and my wife did the inside work with no problem. I found that some people did not understand the concept, and thought that i was nuts. (that is still open to debate, but the shaft thing works)

[jhwelch]

Also, there are no through set screws to match up to a dimple in the shaft on these couplers. It's just the 4 screws on the side to clamp it down and key to hold in place.

If it were me I would want a dimple and a small bolt with a pointy end on that coupler. The top of the bolt would be square with a small hole drilled through it for a length of seizing wire to be inserted and wrapped around the coupling to secure it.

It might make sense to be hauled out for $400 to effect this repair.

-Jonathan

[msmith10]

I'm with Jonathan. I abandoned my plan to use a split coupler and stayed with a conventional 1-piece, but my plans for a split coupler included drilling and tapping for a retaining screw. Not sure why they don't come made that way.

[Dave Neptune]

Protect the shaft!

Use a block of wood or a piece of poly to protect the shaft end when striking with an object like a rock or hammer!!

Dave neptune