MSTS Map Sensor | Crusader R020017 Original Crusader manifold absolute pressure sending unit send air flow measurements to the ECM. Map Sensor Assembly Used with Crusader’s MSTS (Microprocessor Spark Timing System) 3-wire plug-in Original Crusader Replaces Crusader 48004 and 7370200 Replaces Quicksilver 864856A1 Replaces Volvo 3850396 Replaces Pleasurecraft R020017 Replaces OMC 3850396