90121-ZW9-000 Bolt-Washer (6x50) - Overview. The 90121-ZW9-000 bolt-washer (6x50) is a critical fastening component used in Honda marine engine systems. This OEM bolt-washer is specifically designed to secure parts within the water pump and vertical shaft assemblies, ensuring stable and reliable operation of your marine equipment. Manufactured to match Honda's factory specifications exactly, it guarantees seamless integration with existing parts, maintaining optimal performance and durability..