How do you install a prop shaft coupling with only 2" to spare?!

[Project_Mayhem]

I had a new prop shaft and coupling machined. It's a very tight fit and there's only two inches between the transmission's output flange and the coupling. Here are my ideas so far:

• Bolted a piece of plywood to the coupling to protect it, used a ratchet strap attached to the strut to keep the shaft from moving, used a slide hammer to try to install the coupling. I was able to make a little bit of progress but I'm still not sure if it will work
• I've read that you cant push the coupling up against the transmission's output coupling and tap from the inside as damage could occur. There are some unused bolt holes in the transmission housing. I was thinking about bolting a piece of wood and then the coupling would have something to push up against while it's being tapped from the outside
• Heat. I was going to try baking the coupling for at least an hour but unfortunately I couldn't get the stove to light. I can pickup a toaster oven
• Move or remove trans/engine is another option. I'm thinking it'd be easier to slide the engine back than to remove the transmission

This coupling is a really tight fit on the shaft. Feedback on proposed strategies or suggestions would be much appreciated. How did you get yours installed?

 

[dlochner]

This is why split couplings were invented. Replace the coupling with a split coupling is the easiest solution.

 

[Tally Ho]

Do you have a photo?

When I replaced mine, the shaft/coupling interface was tight, especially with the key in place, but not so tight that I needed to hammer it on. A tap or 2 maybe, but nothing dramatic.

What did you decide to use for a shaft seal?

Greg

 

[Hayden Watson]

Split coupling helps and a Sigma coupling makes it dead easy. Heat is your best friend.

 

[jssailem]

My boat was out of the water. I assumed the original engine/transmission shaft setup was proper. I tried to replicate the new shaft and coupling to match the ones I had removed.

The shaft length was determined based on the original one, making the new shaft the proper length for the engine in its original location. With the engine and transmission installed on the mountings, I slipped the shaft forward from outside the boat as the mechanic guided the shaft coupling to the transmission. This allowed me to ensure that the prop and shaft were in the same position under the hull as measured in the original setup.

There was no hammer or heat treatment necessary. The shaft was slipped through the cutlass bearing, shaft log, and new PSS shaft seal. The coupling was attached. The engine and transmission were installed. The shaft and coupling were married to the transmission. I then installed the prop and annodes on the shaft. The initial alignment was set, and the PSS was compressed to allow the boat to be splashed. Once the boat was back in the slip, we again checked that the rotation of the shaft in the PSS and Shaft log was smooth and could be done manually. The final alignment was made, and we got the expected clearances between the transmission and coupler, indicating proper alignment.

Happy Days. I thought I was running in the right direction. There appeared to be a light at the end of the tunnel.

In my case, we then tried to address the water pump issue that appeared when moving the boat back to the slip.
That was the start of the next nightmare.