Split coupling

buzzk · Post by **buzzk** » Wed Jul 21, 2010 4:05 pm

My boat still has the split coupling attaching my shaft to the transmission. I've been looking for a spare shaft and props. I was thinking about going to the 4 blade but I'm going to stick with the 3 blade 23x25 props, I only need a spare when I'm traveling in case I hit something. My shafts are HQ-22. Do any of you have the shaft couplers that are machined to match your shaft? It sounds nice but I would have to buy everything new. Buzz

Donmystic1 · Post by **Donmystic1** » Wed Jul 21, 2010 6:12 pm

I am using 4 bladed props 23 x 23 I replaced all the hardware. I now have new split couplings, shaft logs,shafts and cutlass bearings. The split couplings were machined to the new shafts.

buzzk · Post by **buzzk** » Thu Jul 22, 2010 3:55 am

What HP are your engines? Is your shaft tapered on both ends and do you use a nut that goes over the coupling to tighten down the shaft? Thanks Buzz

buzzk · Post by **buzzk** » Thu Jul 22, 2010 3:58 am

One more question what size shafts do you have? Buzz

Donmystic1 · Post by **Donmystic1** » Thu Jul 22, 2010 9:53 am

My boat has the standard 340 HP mercs. and no only one end is tapered (Prop ). 1.5 inch shafts I found that by trying to push the old shaft out of the coupling using a socket and four bolts on the tranny flange and the old coupling, I pulled the tranny coupling out of round by about 7,000 inch at the bolts. Now I have to re-face the couplings. Thats why I went with the split couplings.

buzzk · Post by **buzzk** » Thu Jul 22, 2010 12:27 pm

I don't really like the slip couplings. It seems to me it would be a lot easier but would cost more to have the coupling and the shaft machined. But I can't afford it right now. I'm looking for an extra shaft not buying two shafts and and two couplings. I was wondering how well the machined coupling to shaft work. Buzz

Donmystic1 · Post by **Donmystic1** » Thu Jul 22, 2010 2:10 pm

They are in use all over especially on sailboats. My machine shop recommended them for ease of removal and to avoid the problem that I had warping the tranny couplings by 7000 in. They have a key way and fit like a glove on the shaft.

John C · Post by **John C** » Sat Jul 24, 2010 4:29 am

The right way is to have a double taper shaft. The trans end is just like the prop end.

IRGuy · Post by **IRGuy** » Sat Jul 24, 2010 7:07 am

I am not sure about if what I have to say is directly applicable to the above but for safety's sake I will mention... A good friend had a Bertram 33 FBC years ago. He wandered out of the channel coming back into his home harbor (Plymouth, MA), and tried to cross a shallow mud bank. He grounded the boat but kept moving as the mud was soft.. but with all the drag on one of his props, the prop shaft slipped out of the coupling that held it to the transmission, and stayed in the mud, leaving him within sight of his mooring but with a 1 1/2" hole below the waterline. Be aware that you need to consider not just the forces on your drive system when you are moving forward (as a tapered shaft does nicely), but you need strong mechanical connections in order to keep everything in place when a rearward force is applied to your props.

Donmystic1 · Post by **Donmystic1** » Sat Jul 24, 2010 7:28 am

I am surprised that the prop and shaft cleared the rudder on the way out. I had to drop my rudder to get the old shafts out and put the new ones in this past fall.

buzzk · Post by **buzzk** » Sat Jul 24, 2010 11:01 am

I've kicked up some mud before but I don't think I would try to push through a mud bank. I don't have to drop my rudder to remove my shaft but I do need to remove my prop. With the right machine shop doing the work, it seems to me that a double tapered end shaft would run much smoother. I know it would be easier to install. Having to use a dial indicator is a lot of trouble to get everything centered. If you could get to everything it wouldn't be to bad. Buzz