Engine Temperature Temp Sensor Sender coolant 3.0 4.3 5.0 5.7 8.1 Mercruiser Temperature Temp Sensor Sender used by Mercruiser, Volvo Penta, Indmar, Pleasurecraft (PCM) and others Replaces Mercruiser 805218T, 805218 , Volvo Penta 3850397 3/8 NPT thread size This is the sendor that goes the guage on dash