The Sierra 18-2381 Upper Drive Unit Cap is interchangeable with the following: GLM 28400, Mallory 9-78121, Mercruiser 94998A2, 9-4998A4, 94998A1, 94998A3. Each Sierra product meets or exceeds the original equipment part it replaces.

Many of the earliest books, particularly those dating back to the 1900s and before, are now extremely scarce and increasingly expensive. We are republishing many of these classic works in affordable, high quality, modern editions, using the original text and artwork.