What I Did
There are various reasons why the centerboard can stick, but mine was because there was marine growth between the CB and the trunk.With it in the water, I put on my scuba gear (I'm lousy at holding my breath) and used a regular Army/Navy Store type machete. I ran it back and forth several times on each side of the CB (with it tied up). I couldn't believe the junk that was coming out of it. When it felt pretty clear, I untied the line, and went back down. It had only come down about 5 or 6 inches.I then took a crowbar, and pulled it free. With the CB down, I ran the machete inside the trunk again, and more junk came out. A LOT more. When no more came out, I move the CB up and down, and it worked cleanly. It's been 4 years, and only one problem since - a time I jammed mud in it when I ran aground.