90402-ZW6-000 Washer Plain (4MM) - Overview. The 90402-ZW6-000 Washer Plain (4MM) is a fundamental hardware component used within Honda marine engine systems. This plain washer supports various mechanical systems by providing a smooth bearing surface and distributing load evenly in critical fastening applications, ensuring reliable assembly and operation of marine equipment. As a genuine OEM part, it adheres strictly to Honda's factory specifications, maintaining the precise dimensions and toler