Lots of centerboard boats have problems with the centerboard and the centerboard trunk. What exactly is the problem? (This is why there is a name for everything on a boat- so you can tell exactly what the problem is!) If the centerboard pin has broken and it doesn''t hold the board proplerly in place so it hinges
up and down, you will have to remove the pieces (including the rubber gaskets or washers that are likely on each side of the centerboard trunk as well) and replace the pin with a new one. This can probably be a simple bolt and washer, though it is best to get one that isn''t threaded its entire length-- a bolt with a smooth top section won''t chew so much into the centerboard as it is moved up and down. It the problem is with the centerboard trunk itself being loose (Your post isn''t exactly clear, and centerboard trunks do get cracked and separated from the boats they''re supposed to be in.) , then you will need to get out some fiberglass. After supporting the hull carefully and putting the trunk exactly where it needs to be, using shores and clamps to hold everything exactly right, you need to grind down the joint between the bottom of the boat (the flat part, in the bilge) and the sides of the centerboard trunk, perhaps 3" or so, all around the centerboard trunk to expose "fresh" fiberglass. Then you need to take a 6" fiberglass tape and lay it, L-shape along both sides and ends of the centerboard: 3" up the side of the trunk and 3" along the bottom of the boat. Then you mix up your fibergllass resin and wet out the whole thing, according to the directions on the resin can. For extra strength, you then do it again. Be sure NOT to cover over the centerboard pin -- you may need to get to it later, sometime. Hope this helps, or please be more specific about your problem!