Mercury - Pitot/Speed Sensor Kit 200 PSI SmartCraft Speed Input 881879A3. Overview. High-speed boats need a tougher, higher-pressure sensor to keep SmartCraft speed readings steady, and that's exactly what this kit delivers. The Mercury 881879A3 Pitot/Speed Sensor Kit is built for vessels running over 80 mph, where a standard pitot sender can't keep up. It mounts on the MerCruiser sterndrive transom bracket or directly on the hull near the engine, giving you a clean, reliable pressure-based spee