In the Catalina 350, Catalina 387, Catalina 400, Catalina 42, and Catalina 440 mastheads there is a pin along with delrin bushings that support the sheaves. There are two sheaves forward and two sheaves aft.

On some mastheads a hollow tube was used as the axle for the sheaves in lieu of the pin and bushings. If that is the case for your masthead, then reuse those tubes, typically a 22 mm outside diameter, and order the replacement sheaves by themselves, part T1961.

Sheaves (4 included):
• Outside diameter: 85 mm (~3 3/8")
• Inside diameter: 22 mm (~7/8")
• Width: 15 mm (5/8")
• Line diameter: 13 mm (~1/2")

Bushings (5 included):
Outside diameter: 22 mm (~7/8")
Inside diameter: 12 mm (~1/2")
Width: 14 mm (~9/16")

Axle pins (2 included):
Outside diameter: 12 mm (~1/2")
Length: 50.5 mm (~2")

Caution: These are the dimensions of the sheaves used in the masthead of the standard mast on the early Catalina 42 with Isomat spars. Owners of Catalina 42's with a furling mast report using the same sheave but with a center bushing machined to 1/2" ID rather than 7/8" ID. The Catalina 400 also used a 1/2" diameter masthead clevis pin. If you need the sheave with 1/2" ID, see part Z3029.

The fifth bushing pictured is used on furling rigs. It is installed over the aft pin to provide a fair lead for the main halyard to connect to the hoist car.