I have internal lines in my boom that run over sheaves at the aft end of the boom. These are for the reefing lines, the topping lift, and the outhaul line. Does anyone know how to replace the sheaves as they are starting to chip and pieces break off. Not an emergency but will need replacing at some point and I'd hate to get a jam when I need to reef 300 miles offshore. This is an O'Day 35 BTW. Thanks, Dave