Make sure that your centerboard is cleated all the way up, and go underwater with something flat like an old saw or a building square, that you can stick in the centerboard slot on both sides of the centerboard. Then try letting the centerboard pendant off and see if it goes down. If it does release, try scraping the centerboard underwater with a wide plastic putty knife if it has a build up of barnacles. You should try to check your shackle and pendant line while you're down there. If you're not up to going underwater, try un-cleating the centerboard pendant line and leave about 6 inches of slack in the line and cleat it back up again. The waves and wakes from other boats going by may possibly free it while she's on her mooring, or take it for a sail and see if she drops. Good luck!Joe