Can't help with specific info on your boat since I have never heard of that model!
But, many boats use delrin or other plastic sleeve bearings to support the rudder post, and these are often enclosed in a rigid tube of metal or FRP. Delrin and many other plastics slowly absorb water
when immersed, and when this happens the plastic expands slightly. Since the bearing is inside a rigid tube, it can not expand outward so instead it is forced inward, reducing the clearance and eventually gripping the rudder post, causing a lot of friction. The only cure is to pull the rudder and either replace the bearings or ream out the extant ones.
Incidentally, I speak from experience here -- our previous boat had this very problem, and twice during the 18 years we owned her I was forced to do the reaming process.