I have one of these beasts too, 1990 model. 23 years of salt water
If you dig out the filler, you will find a bolt and washer threaded into each end of the centerboard pin that holds it in place. If you are lucky, we were not, you can use a punch to push it through to the other side. Make sure that you run a line over the top of the boat, or prop up from underneath, the centerboard so it doesn't clobber you.
What we found was that the pin had fused itself to the keel and no amount of pounding, and boy did we try, was going to liberate that pin.
We wound up drilling all the way through...if that happens to you...that is some tough sledding.
We used the old centerboard as a template and fabricated a new one from 1/2" 314 stainless because we never wanted to do that job again.
We are on the lower Chesapeake and it's a great boat for that area.