87521-ZV0-610 Fuel Petcock Mark - Overview. The 87521-ZV0-610 Fuel Petcock Mark is a vital component within the fuel system of Honda marine engine systems. Its design serves a general but crucial role in marking and identifying the fuel petcock valve that regulates the flow of fuel from the tank to the engine. By clearly marking this valve, it helps operators ensure proper operation and maintenance of the fuel control system. The part is engineered to Honda's OEM standards, ensuring seamless int