Search this website for several threads with pics on how to do it.
FYG, its not hard, provided you're able to lift the boat off her trailer. I did my 23.5 in a boat yard with the boat on stands about 3 feet off the ground. Inside your boat, just aft of the base of the mast compression post, is a plastic cover. Remove that cover to reveal a 3/4 inch stainless bolt. That bolt holds a stainless steel "cassette" in the centerboard trunk. The centerboard pivot axle and sheaves for the control line all are in this cassette. When you undo the bolt inside your boat the cassette and centerboard are free to be removed from the centerboard trunk. Once out you can easily reave a new control line.
On my boat removing the bolt did not cause the centerboard just to fall out. A clever person suggested buying a 3/4 threaded rod (cheap at Lowes) and threading that into the hole where the bolt had been. You then can tap (or whack) on that rod to free up the cassette and centerboard. Before dropping the board think about how you will "catch" the board assembly so that it is not damaged when it comes free. Its heavy...don't expect the Mrs. to do it.
Once out, look at the axle around which the board pivots as well the bushing which protects the board from the axle. My bushing was shot and I was at a loss on where to find a suitable long lasting replacement. I clever person at the yard cut a short section of a cutlass bearing which just happened to have the correct inner and outer diameters. A far superior bush than the original equipment.
When reinstalling, you must be careful to hold the axles in the cassette in place. The usual method is to tape over the axle ends so they can't slide out of position during re-installation.
Hopefully, you haven't thrown out the 3/4 inch threaded rod. Use it as a guide by threading it into the cassette before you re-install the cassette centerboard assembly, thus accurately positioning the cassette/board in the centerboard trunk for the securing bolt.
I know this sounds complicated, but when you get started, you'll find it really is quite easy. If you run into trouble, the folks on this site are most helpful and very knowledgable. Good luck &
Kind regards
Hugh
