I have two solutions having the same assumed issue of pitting at the seal.
while on the dry pull the rudder and put a piece of 1/2 starboard in the cup welded to the shoe that holds the bottom of the rudder. This raises the pitting above the seal. I did this on a 37 worked great!
there is a guy in Sedro Woolly that can repair the upper shaft rather than replace it. I can try to come up with a name and number if you still need it. He repaired one for me on a 32