1985 OMC 65, 100 and 155 HP Models Commercial Service Manual, PN 507450-D, Page 176Get this manual
Sensor Coil Tests Set meter switches to "5" and 5First, check for shortsDisconnect four-wire connectorInsert red meter lead into cavity Attach black meter lead to timer baseCrank engine and observe meter readingRemove lead from cavity "A" and insert into cavity liB Crank engine and observe meterAny reading on either test means sensor coil is shortedLocate short and repair, or replace timer base II