Jeez! I thought I had the only Lancer 28 still afloat.
There aren't any "seals". The rudder stock runs up through a tube, the tube is open on both ends. When mine started leaking it was because the seal (caulking) between the tube and the hull was cracking. I bought a tube of "boatlive caulk" (messy to work with) and dove under the boat and sealed the tube, hull joint with that.It was cold and messy, and I used most of the tube to do it but it held for the rest of the season, I did the job right that fall. I used the Boatlive caulk because it cures under water and stays flexable. Just remember it's the tube to the hull joint, don't get it inside the tube, or you might glue your rudder in place and you won't stop the leak. Let us know how it works out.Good luck.Tom s/v GAIA