The cutlass bearing is not welded in place but rather pressed and then a set screw holds it. When I reshafted our Aluminum 41 Regal from 1-1/2 to 1-3/4 I cut the tubes off the struts and welded on new tubes. The new tubes were purchased from Mc Master Carr of all places. I used the old 1-1/2" shafts with a machined bronze bushing that matched the Id of the tube and the od of the old shafts, which was also the od of the new cutlass bearing. This held the tube as close as possible to the correct alignment during the welding phase. The intent was to not have to line bore the bearing after welding. After we were all done welding and ready for the new shafts to be installed we pushed them up into the correct position and found that even when supported by the end coupling on the engine end, and a centering bushing on the shaft log the strut bearing had been drawn out of positon by the heat of welding. Luckily it was still within the limits of the engine mounts, but it surprised me how the port side moved and the starboard had turned out perfectly! The good thing to know is that today I no longer worry about a shaft shearing because of the Cats' torque when in swells! There are more than enough things to be worrying about on a lengthy cruise without the ones we create by pushing equipment like shafts to their limits! As to shaft log clearance I believe I had 1/4" minuimum. This is also somewhat dictated by the packing glands available for the new shaft diameter. Best of luck with your project. Ps I also bought the johnson cutlass bearings from Deepwater.