We own Westsail 42 hull #1 and had an original rudder built by Fossfoam (which I believe built all the Westsail 42/43 rudders?) Cracks had appeared at the top of the rudder near where the shaft emerges and water was getting into the rudder body. We elected to have a new rudder built as this one was 37 years old... We went to Fossfoam (Florida) and they had the original rudder molds. Upon building the new rudder, it was discovered that the mold did not allow for the shaft to be built with perfect alignment (the upper shaft was cocked back by several degrees) which causes concerns that other boats may also have rudders with the top and bottom shafts not in perfect alignment. This will cause the rudder to flex and eventually will wear out the lower and upper bearings and possibly cause the rudder to fail. Check your rudder for run-out on the upper shaft by creating a reference line where the top of the shaft is accessed, and then turn the wheel port and starboard to see if any run-out is occurring. If it is, you may have one of these defective rudders and you should then confirm that there is no undue wear occurring in your bearing or flexing in the rudderstock causing water intrusion into the rudder shell.
Also, check your retaining bolt as these tend to cause elongation in the quadrant or rudder shaft which will result in some 'play' in the steering. When we had our new rudder built, we elected to have the shaft built of schedule 160 stock rather than the schedule 80 originally specified as this allowed for the addition of a keyway which should keep the quadrant more secure to the shaft.