Prop Shaft Backing Out of Coupler

[jkishel]

Just pulled into Key West and noticed that the coupler (transmission to line shaft) set screws had fallen out and the shaft has backed out of the coupler about 1/4 inch. Now the set screw holes don't align with the dimples on the shaft. Can't move the shaft by hand. Has anyone tried running the engine in forward to drive the shaft ahead with the prop's thrust? Any other suggestions? Thank you.

[Terra Nova]

Originally Posted by jkishel

...Has anyone tried running the engine in forward to drive the shaft ahead with the prop's thrust? Any other suggestions?...

Seriously, if that's all you got, hire a pro.

[billknny]

This is a potentially boat sinking problem.

The very first thing I would do would be to clamp a shaft zinc on the shaft just inside the packing gland to make SURE it can not fall out of the boat.

Everybody already has that, right?

On every boat I have owned those setscrews had drilled heads and could be wired to prevent them backing out, but that horse has already left the barn...

You might need to remove the coupling to get things lined up enough to get them together.

[Cheechako]

You're in Key West! Go overboard and hammer it in! Drill the new set screws heads and wire them so they dont loosen.

[jkishel]

Tied up to a dock and ran in forward gear for a few seconds. Shaft moved ahead about the distance it appeared to have backed out. However, set screws are still not finding the dimples (if there are dimples). Will have to take the coupler/shaft assembly apart to get it realigned as suggested. Thanks gents.

[a64pilot]

It doesn’t have to be exactly precise.
I’d say a 1/4” is well within tolerance. However you don’t want it moving anymore so be sure to secure it.
Maybe slippage mark it, that is fingernail paint stripe across the two, then inspect often to see if the paint mark has broken, which of course indicates slippage.

[FionaJC]

First time I ran my engine in the water the whole engine moved forward 2". Then we tightened the mounts up with weld. Luckily didnt sink.

[Cadence]

Originally Posted by jkishel

Just pulled into Key West and noticed that the coupler (transmission to line shaft) set screws had fallen out and the shaft has backed out of the coupler about 1/4 inch. Now the set screw holes don't align with the dimples on the shaft. Can't move the shaft by hand. Has anyone tried running the engine in forward to drive the shaft ahead with the prop's thrust? Any other suggestions? Thank you.

Loosen the packing gland and try moving the shaft my hand.

[boeing1]

put a hose clamp on the prop shaft to keep it from backing out, then unbolt coupling from transmission and alien on shaft with set screws, then pull shaft fwd and re bolt to transmission, good luck

[RaymondR]

The first thing the pro is likely to do is run the engine in forward gear anyway.

If it slipped out it may be because there were no "dimples" in the shaft to start with.

[SaltyMetals]

This has happened to me twice on two different boats but in my case it was the joint between the plate on the gearbox and the plate on the shaft. Nuts and bolts strewn all over the place. Even if the bolts are partially off you would not notice it in forward (or maybe a little extra vibration). The event will happen when you put the boat in reverse. In each case i was able to pull the shaft forward again to mate with the plate on the back of the gearbox. Yanmar in each case. On the Yanmar the mating between the plates is a matching step on the face of each plate.

You can drill the ends of the bolts and wire them if you like. I either double nut so the second acts as a lock nut or use a nyloc lot. Make sure the bolt is long enough to be sticking out of the nyloc a little since the thread of a bolt is machined to a slightly lesser diameter right at the end and if this is where you expect the nylon bit to hold the nut then it is an accident waiting to happen as it happened to me on a brand new Beneteau. They had not used long enough bolts. Always use locktite on the nuts as well (the red one if you can find it but i think the blue also works well)

JK, in your case are you describing an event where the shaft has actually been dragged partially out of the connector plate? You could try heating the connector plate to then be able to get it off completely and find the correct alignment. It might be a flat instead of a dimple. Meanwhile there was an excellent suggestion of temporarily bolting a zinc anode on the shaft inside the boat so you do lot loose the shaft (and sink your boat....)
Andrew

[Cheechako]

It's amazing how these things will come apart. I did a shaft coupling-stuffing box rebuild in Trini on one boat. Cleaned up everything and painted the coupling, For the coupling I replaced the 4 rusty steel bolts/nuts/lockwashers with SS bolts and Nylok nuts. 2 hours of motoring and the nyloks had come loose , 2 bolts completely out and in the bilge. Clattering like hell. "If it ain't broke, dont fix it"

[Cadence]

Originally Posted by Cheechako

It's amazing how these things will come apart. I did a shaft coupling-stuffing box rebuild in Trini on one boat. Cleaned up everything and painted the coupleing, For the coupling I replaced the 4 rusty steel bolts/nuts/lockwashers with SS bolts and Nylok nuts. 2 hours of motoring and the nyloks had come loose , 2 bolts completely out and in the bilge. Clattering like hell. "If it ain't broke, dont fix it"

I would be more prone to us grade eight bolts for a coupling JMHO

[SaltyMetals]

well, having fixed the Beneteau and my current Jeanneau with bolts of the correct length and nyloc nuts (+locktite) all seems to be good after many thousands of miles. But yr story has caused me to make a note and check my nuts from time to time.
Andrew

[SaltyMetals]

Having done a bit more investigations and having had a new feathering prop fitted with some rather special washers i am wondering if the same washers could be used for the prop shaft connection to the gearbox. These are Nord-Loc washers. They come in pairs . Not quite sure how they work but the engineering company who supplied my prop absolutely swear by them. Most reliable. That of course is the SS Nord-Loc holding the connection between a bronze boss of the propeller and a large bronze nut. It probably bites into the bronze on each side to secure the connection. Could it bite into SS on each side instead? If it can then surely this is the solution to the wretched problem of separation of the drive shaft from the gearbox.
Andrew