16721-ZY9-003 Insulator - Overview. The 16721-ZY9-003 Insulator is a crucial Honda marine engine component that supports the fuel pump system. This insulator functions primarily to provide electrical isolation and reduce vibration between the fuel pump and its mounting surfaces, helping to maintain reliable engine performance and prolong component life. Engineered to match Honda's factory specifications, it ensures seamless integration with existing parts, maintaining optimal performance and dur