Mercury Mariner 200, 225 Optimax Outboards Service Manual, 90-855348, Page 55Get this manual
Ignition System Theory of Operation
When the ignition key is turned to the RUN position, battery voltage is applied to the main relay through the PURPLE wireThe main relay is then closed and D.Ccurrent from the battery or charging system is transferred through the main relay 20 Amp fuse to the positive terminal of all ignition coil primary windingsThe negative terminal of the coil primary is con nected to engine ground through the Electronic Control Module (ECM)When this circuit is closed, magnetic field is allowed to be built up in the ignition coilThe Crank Position Sensor senses the location of the 24 teeth on the flywheel and supplies trigger signal to the ECMWhen the ECM receives this signal, the ECM will then open the ground circuit of the coil primaryThe magnetic field in the ignition coil primary will then collapse cutting across the coil secondary winding creating high voltage charge (50,000 volts) that is sent to the spark plug
Ignition Coils
Inductive type ignition coils are used on the DFI engines