1985 OMC 65, 100 and 155 HP Models Commercial Service Manual, PN 507450-D, Page 151Get this manual
7 To test for shorts, calibrate the ohmmeter to high ohm scaleConnect the black meter lead (-) to the timer base Attach the red meter lead (+) to the "A" terminalthen "B ," thenC," then "0," jumper wire in the connectorAny needle movement indicates the sensor coil or leads are shortedA shorted sensor must be replaced, or the shorted lead repaired to remove the shorted condition8 155 Model onlyConnect ohmmeter black lead to common lead on sensor terminal "0" (port side) and connect ohmmeter red lead to common lead on sensor terminal "0" (starboard side)Meter should show infinity (00), no resistance readingIf meter indicates any resistance readingtimer base assembly must be replaced9Remove the jumper wires from the connector and continue the troubleshooting procedure