Mercury - Gen I Throttle and Shift Cable 19 Foot Mechanical Engine Control. The Mercury Gen I Throttle and Shift Cable is a mechanical control cable designed for boats using traditional Mercury helm controls that require longer routing from the control box to the engine. Built for legacy Mercury Gen I mechanical control systems, it delivers a direct, no-frills connection that keeps throttle response and gear changes smooth, familiar, and predictable-especially helpful during docking, low-speed m