16400-Zz4-023 Throttle Body Assembly - Overview. The 16400-ZZ4-023 throttle body assembly plays a crucial role in Honda marine engine systems. It regulates airflow to the engine, controlling engine speed and performance reliably. Designed for seamless integration with existing components, it maintains optimal performance and durability in demanding marine environments.. Key Features. Genuine Honda OEM throttle body assembly designed to match factory specifications, dimensions, and tolerances.. S