As I'm not familiar with the specifics of the BC23 rudder I hesitate to offer advice, but here goes anyway! Have you checked that the problem is not with the fit of the rudder in the stock rather than the lifting/lowering mechanism? It doesn't take much in the way of muck, foreign objects or swollen wood to make a rudder or centreboard really stiff to move. I had a very small piece of plastic that found its way into my BC26 keel case and jammed the keel in the down position. It took the full power of the electric keel winch with the addition of the spinnaker halyard run to a Pontos winch to get the keel up, very slowly. I spotted the errant piece of plastic once it was up, removed it and everything was back to normal. If there's any way that you can remove the rudder blade from the stock then I'd try that first and give it and the stock cheeks a good clean. As I said, not being familiar with how well SY have buried the system in the back of the boat it may be easier said than done.
Nick
