90504-ZX2-C00 Washer (Upper) - Overview. The 90504-ZX2-C00 Washer (Upper) is a genuine OEM Honda marine part essential for the proper mounting and secure fastening within Honda marine engine systems. This washer part supports the mechanical assembly system by providing precise alignment and stability, ensuring the reliable operation of your marine engine components. Crafted from robust materials, it guarantees resistance to wear and tear within the demanding marine environment, ensuring seamless