I assume the existing rudder is inboard with a shaft coming up through a shaft log, then thru the quadrant. You can pull the rudder at your next haulout, or sometimes you can pull it out in the
water if the shaft log is well above the waterline. With the rudder on sawhorses, drill some holes all the way through, just aft of the rudder shaft. If you hit metal, STOP DRILLING. This will tell you if your have a wooden rudder, solid
fiberglass, or foam
core, as well as if there is seawater infiltration. If things are wet, you may be getting some damage to the rudder straps internally. Or, you can just bite the bullet and remove all of the rudder material, leaving only the rudder stock and straps, then
rebuild it after confirming there is no damage to the stock itself. It sucks, but it has to be done for you to have confidence the rudder will last another forty years. Or, go for an
outboard rudder. Easier to maintain, greater
steering power than a balanced rudder, and not too difficult to build.
The Searunners use a short (one foot long) stainless tiller arm, slightly offset, that connects to either a push-pull cable. or, in my case, an
Edson pedestal, monster sheaves and Amsteel synthetic cable connected to the tiller arm end at the back of the sterncastle.