Rudder stuffing box
Just did this on my 1986 C30. Get access by removing the panel at the rear of the quarterberth and remove the 3 bolts holding the upper metal ring in place on the rudder. Pull this up the rudder shaft to expose the flax and remove with a sharp knife or awl. What came out of mine was a single ring of 5/8" flax that fit exactly the space available. Trouble was, even with a new 5/8" teflon flax, there was very little adjustment. I then installed two rings of 1/4" (joints opposite each other of course) and then compressed these into place. Much better fit - and really easy to do.