How to tap on new split coupler on shaft

[jsgonz]

I have a Hunter 28.5. I have installed a new strut and replaced the 1" shaft with a stainless steel one and am installing the PYI packless shaft seal (PSS). I have the shaft thru the strut and shaft tube and now have the PSS installed (not tightened) but the new split coupler now must be tapped on the engine side of the shaft but it has a very tight fit and will require a non-marring hammer to do it. The problem is that I have no room behind the transmission between the output flange and coupler to swing a tapping hammer with sufficient force to fit in the coupler to the proper location on the shaft so that I can complete the installation and align the Yanmar properly.

I read where someone had to remove the engine to insert the shaft from inside the boat after tapping in the coupler. I hope that is not what I will be facing. I see no way to do it inside the boat with the limited room. It will take forceful tapping to get the coupler on the shaft. Any suggestions out there will be greatly appreciated.

 

[Alan]

Use a machinist trick. Pack the shaft end in dry ice and heat the coupling half with a torch. The coupling will slide on easily. Use a pair of gloves to make it easy on your hands.

 

[jsgonz]

Thanks Alan, good suggestion. I have talked with Deep Blue Yatch Supply who sold me the shaft and coupler. The shaft has been "faced" for the coupler so it has been on the shaft once when this was done. They suggested that I hammer in steel wedges on the split portions of the coupler ( one on either side ) before placing it on the shaft. This should open it up some. I will do that but will also try the heat/cold treatment in addition if it is still too snug of a fit to slide on. As I mentioned, I have no room to tap it in with a hammer to encourge it on so any suggestions are appreciated.

 

[Alan]

You will find that if you use my suggestion there will be no need for any hammering at all. The ID of the coupling will have increased with heat added. The OD of the shaft will have decreased with the cold (lack of heat) which will result in a loose fit of the two parts. Of course you will want to move quickly before they equalize their temps.

 

[jsgonz]

Alan, how long should I heat the coupler and how much time should I have the dry ice on the shaft? Do I put the ice directly on the shaft? Do I also heat the keyway as well?

 

[Alan]

Yes you can pack the dry ice directly around the shaft. It will disappear as a gas as it warms. The key should be cooled on the shaft. I would cool it for 20 minutes or so. You will be surprised how easily it will come together. Heating the coupler will be much quicker.

 

[jsgonz]

Thanks for the tip using dry ice on the shaft and heating the coupler with a propane torch. I was able to get it on. At first it still did not go onto the shaft far enough so I tapped it hard at the prop end and then it went too far. I had to back it off to the proper location using a socket in the middle and tightening four bolts on the shaft but it is there now.

Next week, I will re-align the engine and then attach the R and D flexible coupler between the output flange and the coupler. I barely have room on the shaft to install it. When all is put together, the aft end of the new coupler will be an inch away from the rotor bearing on the PSS seal. It is crowded but I think it will be ok.

But I would like not to install it if I don't really need it; however, I would like to hear from anyone who has installed the flexible coupler and is a big proponent of it. Thank you Alan for your help, the machinist trick did work, and anyone who will share your experience with the R and D Flexible coupler.