Cutlass
If the cutlass bearing wears through the rubber part, it can score the shaft to the point of needing a new shaft. Further wear can damage the strut and/or damage the shaft log itself. You don't want to get into replacing either the strut or the shaft log.
If the cutlass bearing is worn to the point where there is considerable shaft play at the strut, you're probably not doing the transmission any good either. If the shaft has enough play, it may be damaging the shaft log or the shaft seal. It's like having the shaft misaligned. The vibration is the shaft flopping around under there.
The cutlass bearing can be pressed out (and the new on back in) without removing the shaft, provided the shaft is clean enough but it is a project usually done with the boat out of the water. While it won't be easy underwater, it can likely be done by an experienced diver/repair man. The pressing tool while not complicated does have several parts that can and do fall out. You sometimes need six hands to get everything lined up and tightened up such that it doesn't need holding anymore. Not a big deal on dry land but a pain in the 'roids under the water.
You'll have to remove the prop, of course, not a big deal on a fixed prop but some folding and feathering types require considerable disassembly and more potential dropped parts. Also note that there are a couple of allen head (usually) set screws holding the cutlass bearing in place. Sometimes these are corroded to the point of needing to be drilled out.
My cutlass bearing would not come out despite having two different pressing tools (not to mention various hammers) The mechanic finally cut it out after removing the shaft. The problem with mine was that the strut is so long (almost 7 inches) that the cutlass bearing was inserted in two pieces. Pressing the forward end of the bearing towards the aft end caused the two parts to bind.
If you have to cut it out, you will need to remove the shaft first, not recommended underwater.
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