I'd give Rudy at D&R Marine a call (508) 644-3001, he is THE parts guy for our O'DAYs. He was the Parts Dept. Manager at O'DAY from 1973-89 and now runs a little one-man shop in Assonet, MA making and selling the stuff we need. He may even have the gaskets in stock ready to ship. Otherwise he can tell you how to fix the CB pivot leak based on his knowledge. If your 15 has a pivoting CB, that would make it one of the ones built in the early 1970's, just as Rudy was starting at O'DAY, but he should still have some knowledge about the boat.