I decided to change the rudder since the old one was compromised. I ordered new rudder from Jeffa marine, coated it with 7 layers of Gelshield 200, and top it with antifouling. Looks good. Jeffa recommend changing of the seal of Sika 221 around the shaft at least every 3 years to avoid osmosis. The old one was with osmosis and the previous owner has thought that it is a good idea to drill a lot of holes in it and to fill it with sikaflex.