90507-ZW1-003 Washer, Plain - Overview. The 90507-ZW1-003 Washer, Plain is a critical hardware component designed for use in Honda marine engine systems. This plain washer serves an essential function in load distribution when fastening components, ensuring that parts remain securely in place and preventing damage caused by localized stress. Engineered to Honda's factory specifications, this washer maintains the durability and reliability required to support various systems within the marine eng