Get rid of the grommet
The pennent line for the centerboard on my 23 comes out into the cockpit on the bridge deck step. To make a tight fit around the line, the hole is fitted with a white plastic grommet that surrounds the line. The first time I tried to insert a steel rod through this hole to free my stuck centerboard, I couldn't get it to fit into the hole past the line. However, once I removed the grommet, I found the actual hole and passageway to be more than wide enough to accomodate the line and the rod. The grommet on my boat is attached with one or two screws, and comes off quite easily. I would also echo Justin's caveat to be careful. You might want to add a "cushion" of sorts made of wadded up tape or some type of material at the end of the rod so that you don't have a 3/16 inch spear poking a hole in your centerboard. Once you take the grommet off, you will be able to see how big a cushion the hole will handle. I might add that I had to hammer on the end of the rod to get my centerboard free; I did not use a cushion, and there was no damage to my centerboard.