Prop Shaft question

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Duane
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Prop Shaft question

Post by Duane »

When I pulled my boat out last fall, I drove up to the trailer and tried to run it up on the trailer but got it a little crooked so I was going to back it off and try again. When I put it into reverse, I had no transmission??? I ended up pulling the boat up on the trailer by hand and hauling it out with the car. When I looked into the engine hatch, I see that the prop shaft had pulled out of the transmission. I found a square key in the bilge that has fallen out. Can anyone tell me how this goes back in and what secures the square key?

Does anyone have a photo or picture from a manual as to what this looks like in the boat? It was dark when I hauled it out and I dont seem to have a photo of this area of the boat or a manual that I could look at. Can anyone help in this area? I am thinking that the shaft fell out of the coupling box (I guess I didnt know the difference between the transmission and the coupling box). I would like to see where the key is placed.
Last edited by Duane on Wed Feb 12, 2014 5:13 pm, edited 1 time in total.
larryeddington
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Re: Prop Shaft question

Post by larryeddington »

Are you sure it pulled out of transmission or did coupler pulled off of the shaft. The coupler is most likely a a press fit on the shaft with two set screws holding with a dimple under in the shaft and a key and matching keyway in both shaft and coupler. I think the part that goes in transmission has a nut on it and is splined.

A propeller shaft can be lost out the back when that happens. Some install a stainless ring on the shaft between coupler and stuffing box to prevent a disastrous loss of shaft and huge incursion of H2O in the event of coupler pull out.

There are other kinds of couplers but I think most of our F boats have the press fit kind.
Larry Eddington
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Big D
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Re: Prop Shaft question

Post by Big D »

Sounds like the shaft pulled out of the couppler. Larry is right, there should be a couple of set screws going through the coupler that mate with a couple of dimples in the shaft. These prevent the shaft from pulling out. Typically, the set screws have square heads with holes through them so that wire can be used to prevent them from turning after being tightend so they don't loosen off. If you don't see these screws but see two threaded holes in the coupler, that's you're problem, and the screws are likely in the bilge somewhere. There is a keyway in the shaft and coupler that the key fits into. The key and the shaft-to-coupler should be a snug fit with no play. This is where I usually advise checking the alignment. Did you ever feel any vibration while under way?
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P-Dogg
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Re: Prop Shaft question

Post by P-Dogg »

Some install a stainless ring on the shaft between coupler and stuffing box to prevent a disastrous loss of shaft
You can also achieve a similar result by installing a shaft zinc close enough to a shaft strut that it keeps the shaft from coming all the way out if the coupling fails. The caveat is that if you zinc dissolves completely, which would not be readily apparent, so does your shaft retention. And too close may impede good water flow to the cutlass bearing.

You can get split shaft collars from my favorite store on earth, McMaster-Carr. http://www.mcmaster.com/#split-shaft-collars/=qmke79

I like to read a lot. One thing that I read recently was (yet another) boating disaster book. A cruising sailboat got their wheel caught in a net while they were motoring. It pulled the shaft out of the boat, which subsequently sank in short order. I guess that I should quit typing and buy my own dang shaft collars....
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Stripermann2
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Re: Prop Shaft question

Post by Stripermann2 »

Here ya go...all the hardware you need for the shafting system.

http://www.buckalgonquin.com/shafting-accessories
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