90405-ZY3-000 Plain (8mm) Washer - Overview. The 90405-ZY3-000 Plain (8mm) Washer is a vital hardware component used in Honda marine engine systems. It serves as a flat, ring-shaped washer designed to evenly distribute the load of fasteners and prevent surface damage during assembly. This washer supports various mechanical fastening points in the rigging and accessories system, helping maintain proper tension and reliable connections throughout the engine's operational life. Engineered to Honda'