Mercury Mariner 30/40 4-Stroke Outboard Service Manual 1998, Page 69Get this manual
IGNITION
Flywheel Assembly
The flywheel assembly contains six permanently charged magnet segments which are bonded and retained to the inner wall of the flywheelEach magnet contains north and south pole providing 12 pole system
Ignition Coils
The primary (+) side of the ignition coil receives voltage discharged from capacitor in the ignition (C Olcircuit located inside the ECMThe voltage is multiplied by the coil until it can jump the spark plug gapEach ignition coil will produce high voltage spark at each crank shaft revolutionproducing spark at each cyli nder at the proper time (predetermined by the ECM)Ignition coil maximum output is approximately 40,000 volts