Although Catalina Yachts MAY sell halyards:
DO NOT BUY THEM THERE! The stock halyard on the Catalina 30 (and the 320, and most likely all Catalinas) is Yale UULS. It has very good and strength and stretch characteristics. However, the cover is so loosely woven that you will get hernias where the core poikes through the cover with great frequency. I don't know anything about the Sampson ULS line that is sold on this site, but it's probably fairly good dacron line. You will need 3/8" for both halyards (not 7/16 as recommended here).I no longer have my C-30 manual (since I sold the boat), but the recommended lengths and diameters of the halyards, sheets, reef ines, etc are all specified in your manual. As I recall, the main halyard is aboout 105" of 3/8" and the genoa / spinnaker halyards are 110' of 3/8" low stretch double braid dacron line. Typically, the genoa and the spinnaker sheets are two times the length of the boat, which would make them 60' each.SteveAlchemist C-30T #4764Alchemist C-320 #909