Solid coupling issues.

[Mick & Denise]

I have noticed that my shaft has slid out of the coupling about 5/8". It is a solid coupling. it does not have a visable cross pin to hold it in the coupling but does have a hole that you can see into. it almost looks like there is a step turned on the shaft so it cannot come out of the coupling. both the port and starboard sides are about the same now as far as the amount of key that sticks out of the coupling. Can anyone tell me how the shafts are held in? Is it a possibility that the shaft has been in too far since assembled and finally under a heavy reverse load came out to where it should be? Thanks for the input. 50 ft Sundancer with 3176's and V drives. 2" shafts

 

[tobnpr]

That's scary IMO...

Sounds like you're missing the set screw that holds the shaft in place in the coupler and prevents the shaft from backing out in reverse.

When you say it has a "hole" that you can see into, does it look like it's tapped for a set screw?

I'll relate a little story...
I once ran my Chris-Craft inboard aground on a sandbar and bent the shaft. I picked up a replacement shaft which was not dimpled for the set screw. I drilled the shaft myself and inserted the set screw and went happily about using the boat. About a month later we were fishing offshore and I reversed hard at one point, much harder than when needing reverse around the dock. I heard and felt a "clunk", suddenly my RPMs shot up, but the boat wasn't moving. Pulled the hatch and the shaft had backed completely out of the coupler AND the stuffing box and I was taking on water- fortunately the rudder prevented the whole shebang from dropping 80 feet to the bottom. Luckily for me it was summertime, I jumped overboard and shoved the shaft forward back through the stuffing box and into the coupler. Once aboard, I put her ingear which shoved the shaft the rest of the way into the coupler. I lined everything up again and tightened the set screw. Needless to say I didn't hit reverse again that day until docking, and then VERY gingerly... I didn't drill the dimple in the shaft deep enough for the set screw to grab properly.

I've never heard about an assembly that is designed to shift/move. Call your boatyard to discuss.

Don't mess around with this, it could result in a very bad day...

 

[Mick & Denise]

There is a hole that is tapped near the flange end of the coupling. It seems to go into a counterbored area in the coupling. On a straight shaft with a solid coupling is the shaft threaded on the end so you can put a nut on it after it goes thru the coupling? The nut would go into the counterbored area and stop the shaft from coming out? I have not separated the 2 couplings to see what is going on in there. Since there is no cross pin i figured it had to be held into the coupling by means of a nut on the transmission end of the coupling. If I cannot get the configuration from someone on here I will take it apart to find out why it slid back. Thanks for the input.

 

[tobnpr]

I'm not familiar with V-drive transmissions ( I didn't even know they used V-drives on 50 footers!). I can tell you that on straight drives what I think you're referring to as a "counterbored" area on the back of the coupler is relatively shallow (definitely not deep enough to put a "nut" on the back of a shaft) and is there to align/mate the coupler properly to the transmission. I have no idea if or why a V-drive coupler would be different- but straight drive couplers are mated/machined to the shaft. The interior bore of the coupler is tapered- and the shaft needs to be machined precisely to that taper so the shaft will not extend beyond the rear face of the coupler. This is so that the thrust from the prop/shaft is distributed over the coupler- and not the end of the shaft poking into the transmission. The shaft has a female keyway and the coupler a corresponding male keyway to keep the shaft from spinning within the coupler. Then the shaft is drilled / dimpled so that a set screw can be placed through the coupler and into the shft to prevent it from backing out when the transmission is reversed.

Obviously couplers for your V-Drives are not set up this way, so I'll shutup now...

 

[geriksen]

You are both correct. They can be made either way. (dimples and set screws or tapered with a nut in the counterbore)
I had your identical boat and I just looked at pictures I had from my survey and there are no set screws so you must have the nut inside.
I would separate the coupling halves and check that nut before you run the boat again.

 

[Mick & Denise]

Geriksen, Thanks for the info. I am figuring the either the nut backed off or strange as it may seem when it was assembled it was so tight in the coupling that after the shaft was put thru the coupling the nut was tightened but the shaft was never pulled back so the nut hit against the counterbore. Thats the only other possibility I can see and now the key sticks out of both the port side and starboard the same amount. I will separate the coupling to be sure though. As tobnpr mentioned better now than out in the ocean. Thanks to both of you. And Geriksen, impressive line of boats you have had there.