Unless your boat has been modified, there is no bearing in the rudder shaft tube of a Cal 2-27. It was simply glass laid up around a waxed shaft. When it wears, which it will, the fix typically involves dropping your rudder, applying a thick layer of wax to it so that epoxy or resin will not stick to it, and filling the space around the rudder shaft in the tube with new epoxy or polyester resin.
To do that one drills a hole horizontally into the shaft tube near the base at the hull and three more holes near the top of the tube, below the shaft gland, at 120* from one another. One then reinserts the rudder shaft into the tube and trues it vertically, to the extent possible, and packs plasticine clay around the shaft where it emerges from the hull above rudder blade to block the tube. Then, screw a zirk fitting into the hole in the tube near the base and pump lean epoxy or resin into the tube through that until one sees it emerge from the holes near the top of the tube. When that shows up, block the holes with a short screw or peg. Once the drips of resin that emerged from the holes near the top of the tube begin to "green", you can remove the zirk fitting from the bottom and replace it with a similar sized machine screw with a little epoxy on the threads that will lock it in place forever. The wax on the rudder shaft prevents the epoxy or resin from adhering to it and the holes in the tube are sealed by the epoxy or resin. Once the epoxy or resin has thoroughly set up, you can work the rudder shaft back and forth a few times to ensure there is no adhesion to that.
The foregoing technique was used to restore the rudder shaft tube on a 1976 Cal 2-29 we used to own, which has, essentially, the same construct as the 2-27 and it worked very well.