This plastic sheave for wire halyards is used at the masthead of a Catalina 25 and Catalina 27. It is also used in both the boom end and gooseneck castings as an wire outhaul sheave on the Catalina 28, Catalina 30, Catalina 34, and Catalina 36.
1) Will not fit C-27s with hull numbers in the following ranges: 1421-1450, 2465-2549, 3101-3150, 3950-3999, 4701-4725, 5042-5051, and 5140-5149. These boats were not built in California and used a different mast. There may be other ranges as well that we have not discovered yet.
2) Although machined with a groove large enough to fit 3/16" wire, the 2" O.D. is too small for us to recommend this sheave for any wire larger than 1/8" 7X19. If used with a larger diameter wire, the small diameter of the sheave will tend to kink the wire as the wire rolls over the sheave.