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Prop Shaft, Stuffing Box & Cutless Bearing
Most sailors treat the running gear (stuffing box, cutless bearing and shaft) as low- or no-maintenance items, but they deserve attention. A leaky stuffing box can allow a truly irritating amount of water into the boat, while over-tightening of the packing gland will cause excessive wear, necessitating the replacement of a $500 shaft.
Running gear pictorials
This site covers a wide range of running gear issues, including
generally in greater detail than we do on this site.
Cutless/cutlass bearing replacement
For what it's worth, the industry-preferred spelling is "cutless" but both
spellings are used (to confuse search engines). Gerard Warner replaced his bearing with a:
These specs turn out to be identical with the specs (measured externally with a caliper gauge) for a Mk I, a Mk IV and a mid-run C&C 30; clearly, when C&C found something that worked they stuck with it.
Stuffing box maintenance
Traditional packing for a stuffing box is wax- or grease-impregnated flax that looks somewhat like squared sash cord. The correct size is 1/4". Earlier it was suggested here that 5/16" was also an option, but the consensus on the Forum is that while this is possible, 1/4" is better. Two rings go on easily, one person reported that he would put a third on once the first two had compressed a bit.
As built, 27's had several rows of flax packing in a stuffing box like the one above. A stuffing box should be just tight enough that it does not drip when the shaft is motionless, and drips two or three drops per minute when the shaft is turning (necessary because the water lubricates the packing). With packing in good condition, this is firmly hand-tight. You do need two large wrenches, though, to set the lock-nut, without which the compression nut will loosen and perhaps come off, which will sink your boat.
In the time since our boats were built, alternatives have appeared that are drier, probably more durable and less likely to cause the damage visible on the scored shaft above. These are:
Which to choose?
According to a post on another sailing site, it is possible (though probably still not fun) to replace the packing in your stuffing box on the water. Undo the lock-nut and release the compression nut from the body. Tie a length of bicycle inner tube tightly around the stuffing box body and shaft. This should at least keep the water from gushing in while you replace the packing.
Another source suggests that you should loosen (one at a time), rotate and inspect the hose clamps every few years as drips may collect on the unseen underside and cause corrosion. Given the reliance on a single clamp at the packing gland end, this seems a reasonable precaution.