90303-ZV5-000 Special (12mm) Nut - Overview. The 90303-ZV5-000 Special (12mm) Nut is a crucial component in Honda marine engine systems, playing an essential role in securing mechanical assemblies reliably. This special nut is specifically designed to support the rigging and accessory systems involved in the efficient operation of Honda marine engines. By securing parts tightly and flawlessly, it ensures seamless integration with existing parts, maintaining optimal performance and durability.. K