1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 20Get this manual
Description The outboard ignition system is alternator-driven with distributor-less capacitor dischargeMajor components of the ignition system are the flywheel, stator, trigger, switch box, ignition coils and spark plugsThe stator assembly is mounted stationary below the flywheel and has capacitor charging coilsThe flywheel is fitted with permanent magnets inside the outer rimAs the flywheel rotates the permanent magnets pass the capacitor charging coilsThis causes the capacitor charging coils to produce AC voltageThe AC voltage then is conducted to the switch box where it is rectified and stored in capacitorThe trigger assembly (also mounted under the flywheel) has coilsThe flywheel has second set of permanent magnets (located around the center hub)As the flywheel rotates the second set of magnets pass the trigger coilsThis causes the trigger coils to produce an AC voltage that is conducted to an electric Silicon Controlled Rectifier (SCR) in the switch boxThe switch discharges the capacitor voltage into the ignition coil at the correct time and firing order sequenceCapacitor voltage is conducted to the primary side of the ignition coilThe ignition coil multiplies this voltage high enough to jump the gap at the spark plugThe preceding sequence occurs once-per-enginerevolution for each cylinderSpark timing is changed (advancedretarded) by rotating the trigger assembly which changes each trigger coil position in relation to the permanent magnets on the flywheel center hubIMPORTANT: If the engine misfires, runs rough or does not start, the ignition system should be checked using Multi-MeterDVA Tester (91-99750), or voltmeter (capable of measuring 400 volts DC, or higher) and Direct Voltage Adaptor (91-89045)