Seems you may be embarking on a rather expensive endeavor if you choose to cut the shaft. As you know it's stainless steel and won't be cheap to replace
I'll start with the old cliché - if it ain't broke, don't fix it.
What could be wrong with the shaft. Do you suspect it might be bent. Do you think you have an electrolysis problem between the propeller and the shaft
Aside from the above, there's not a whole lot that can go wrong with the shaft. It rides in a piece of rope at the stuffing box and a rubber/plastic bearing at the cutlass. It's doubtful the shaft is worn
My suggestion: disconnect the shaft from the engine at the coupling (mark it so you can bolt it back in the same rotation you took it apart).. Rotate the shaft by hand - if it rotates feely it probably isn't bent. Check the gap between the engine coupling and the shaft coupling. There shouldn't be more than a few thousands difference. Rotate the shaft - again the clearance should be within a few thousands as you rotate it. If there is a huge variation as you rotate the shaft, then the shaft is probably bent. If there is a difference in clearance but is the same as you rotate the shaft - you have an alignment problem between the engine and the shaft
Pull the prop. check the treads and check for electrolysis. If there is any electrolysis, it should be in the prop not the shaft When you are all done, replace the 4 coupling bolts with stainless steel bolts and SS nylock nuts
