Mercury - Gen I Throttle and Shift Cable 20 Foot Mechanical Engine Control. The Mercury Gen I Throttle and Shift Cable is designed for boats using traditional Mercury mechanical control systems that rely on a direct, hands-on connection from the helm to the engine. Built for legacy Gen I control interfaces, it delivers predictable throttle response and clean gear engagement without electronic involvement. The 20-foot (6.1 meter) length is a practical choice for longer console-to-engine routing,