Mercury - Gen I Throttle and Shift Cable 21 Foot Mechanical Engine Control 8M0082494. The Mercury Gen I Throttle and Shift Cable (21 Foot / 6.4 m) is designed for boats using traditional Mercury Gen I mechanical control systems. This cable connects the control box to the engine to deliver direct, responsive throttle and shift movement without electronic involvement. The 21-foot length is ideal for wide-beam boats, deeper hulls, and long helm-to-engine routing where added distance supports clean,