Mercury – SmartCraft Authentication Device | Third-Party Gauge Interface | 8M0105518Mercury SmartCraft Authentication Device Third Party Gauge Interface 8M0105518 Overview Some third party gauges can read SmartCraft data, but they need the right handshake from the engine before those features come alive. The Mercury 8M0105518 SmartCraft Authentication Device provides that authorization, allowing applicable Medallion, FW Murphy, and similar gauges to communicate properly with both mechanical and Digital Throttle and Shift MerCruiser