O'Day 25 keel centerboard
Lloyd,
As Dave said, Rudy Nickerson is the guy to talk to about purchasing a centerboard for your 25. The boat will sail without it, but it will sail a whole lot better and point up higher with the centerboard. I'm not familiar with the 78 OD 25, but I sailed a 1975 OD 25 years ago, and had the chance to check out the centerboard underwater. My friend's boat had the centerboard winch and cable mounted on the table stanchion down below. I'm pretty sure that the board is fiberglass because I hefted it when I checked it out underwater. There are two fiberglass wedges that support the 1" fiber pin that the centerboard pivots on. These wedges fit in triangular rabbet grooves and are caulked in place. Then you have two stainless steel plates that fit into rabbet grooves at the bottom of the keel that go against the bottom of these wedges. The plates are held on with four 1/4" Phillips head machine bolt which are approximately 1-5/8" long. Also, there are two wood screws that go through these plates and into the bottom of each triangular wedge. Make sure that the holes under the keel for the plates are still in tact and have no broken bolts in them. I believe that the leaded keel on your boat has some kind of Stainless Steel threaded Molly type fittings in-bedded in the lead for these bolts, but I'm not sure. I think that Rudy could give you more information on that than anyone else. He worked in the O'Day plant years ago. Anyway, these are the things that are also needed beside the centerboard. Here's a picture of what my keel slot looks like on the OD 222. I'm not sure if there is a small sheave up in the keel slot of your boat, but mine has one up top in a small recess. Good Luck!
Joe