Threaded rudder post collar - what is this?

[MondayNever]

Hey all, just bought a new old boat (1995 Contest 46) and I’m digging into the many projects at hand. On the sea trial we noted that there was some sea water leakage into the boat at the rudder post when we were squatting the stern down while running at WOT (with our way overkill 135hp). On further inspection, there is a threaded plastic collar that encompasses the shaft at the top of the rudder tube. This unit can be tightened down, which I have done. I have not taken the boat back out to test whether tightening stopped the leak yet.

My question is: what does this collar do? Is this essentially a packing gland? Is it possible that there is a flax ring filled stuffing box below the collar? If so, is there a limit to how to tight the collar should be (given that it’s a slow moving shaft, unlike a prop shaft)?

Here are pictures of a spare collar that I found laying around. Hopefully someone more knowledgeable than me will be able to immediately identify its function, but if not I can pull apart the panels behind the aft berth to get pics of the entire rudder assembly.

Thank you cruisersforum hive mind!

[Lepke]

The rudder shaft will have a seal. sometimes just like the prop shaft. Because the top of the rudder shaft housing is usually above the waterline, the packing will sometimes dry out and allow leaks.

[nhschneider]

My 1984 Contest 48 has a similar setup. On mine, there was flax packing that sealed tight for many years. However, we did develop a significant leak during our 49,000-mile circumnavigation. While we were hauled out, I removed the plastic ‘nut’ and had a new one fabricated that had two grooves for o-rings machined on the inside bore. I dug out the old packing and packed as much silicon grease in the cavity as I could fit. Then I installed three new rings of Teflon packing, with each ring’s mating surface offset from the next by 180°. We’ve put about 10,000 miles on it since that repair and it hasn’t leaked a drop.

Congratulations on your new-to-you boat. We love our Contest and we hope you enjoy yours.

Fair winds and calm seas.