16400-ZY3-A03 Throttle Body Assembly - Overview. The 16400-ZY3-A03 Throttle Body Assembly is a critical part of Honda marine engine systems. This component regulates the airflow into the engine by controlling the throttle plate, directly impacting engine performance and power output. Designed to meet strict factory specifications, it ensures seamless integration with existing parts, maintaining optimal performance and durability.. Key Features. Genuine OEM Honda throttle body assembly ensures pe