Mercury - Pressure Transducer Kit 100 PSI SmartCraft Speed Input 859210A1. Overview. OptiMax engines rely on a steady water-pressure signal to deliver accurate SmartCraft speed readings, and this kit provides exactly that. The Mercury 859210A1 Pressure Transducer Kit gives your engine a clean 100 PSI pressure input by plumbing the sensor to a speed-pickup tube and wiring it directly into the SmartCraft sensor plug. Mounted on the transom bracket or in a nearby hull location, it gives boats runni