This sheave is supported by a tube that passes through the masthead in the Catalina 34 and Catalina 36 furling rigs. This sheave does not use a bushing when used on the Catalina 34, and Catalina 36.

In the Catalina 350, Catalina 380, 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.

Below is a Inventory of the usage:
• (6) per Catalina 34 masthead in-mast furling rigs
• (4) per Catalina 350 masthead in-mast furling rigs
• (4) per Catalina 350 masthead non-furling rigs
• (6) per Catalina 36 masthead in-mast furling rigs
• (4) per Catalina 380 masthead in-mast furling rigs
• (4) per Catalina 387 masthead in-mast furling rigs
• (4) per Catalina 387 masthead non-furling rigs
• (4) per Catalina 400 masthead in-mast furling rigs
• (4) per Catalina 400 masthead non-furling rigs
• (4) per Catalina 42 masthead in-mast furling rigs
• (4) per Catalina 42 masthead non-furling rigs
• (4) per Catalina 440 masthead in-mast furling rigs

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

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 #F8121.