The Cutless bearing is actually a bushing in the strut that holds the
prop shaft on some boats. Not all sailboats have one. When the boat
is out of the water, grab the prop and shake it from side to side. If
it goes THUNK THUNK, it needs replacing. If it just goes rattle
rattle, its still ok. To get an education, go around the boat yard
shaking the props on various boats and you will get a good idea of what
is good and bad. There are an amazing number of boats out there with
worn out cutless bearing and maybe it is not a problem for them.