87521-ZVA-000 Mark Fuel Petcock - Overview. The 87521-ZVA-000 Mark Fuel Petcock is a genuine OEM Honda part that supports the fuel system in Honda marine engine systems. Serving as a visual reference for the fuel petcock valve, this mark helps operators quickly identify the fuel control position for reliable engine operation. Designed to exact factory specifications, it ensures seamless integration with existing parts, maintaining optimal performance and durability.. Key Features. Visual indicat