My cutless bearing (Vetus stern gland) has a tube which vents into the weed hatch chute (Tim Tyler hull) at or just above the waterline, as recommended by Vetus. It occasionally decides to tighten up, make horrible squealing noises and get hot, often just after setting off on the first post-winter trip, but it's done it occasionally when out cruising, for example when a lot of mud has been churned up going astern and presumably got into the bearing. I've found the fix is to take off the vent tube (unscrew from spigot on weed hatch), attach a hose to it, and flush some water through it from the tap with the prop turning slowly, this usually fixes it for the rest of the trip.
