1986+ Mercury 6/8/9.9/10/15HP 2-stroke Factory Service Manual, Page 63Get this manual
IGNITION SYSTEM
Description
The ignition system is an alternator driven capacitor discharge systemMajor components of the ignition system are the flywheel, stator, trigger coil, switch box, ignition coils and spark plugsThe flywheel has permanent magnets mounted in both the outer rim and the center hubThe BLACK stator assembly is mounted below the flywheel and has low speed (LS) and high speed (HS) capacitor charging coilLow speed coil provides primary voltage to the switch box from idle to approximately 2500 RPMThe high speed coil provides primary voltage from 2000 RPM to the maximum RPM the outboard is capable of achievingThe RED stator assembly is mounted below the flywheel and has only one capacitor charging coilAs the flywheel rotates, the magnets mounted in the flywheel outer rim pass the charging coils creating voltageThis voltage is rectified to DC and charges the capacitor located in the switch boxAs the flywheel continues to rotate, the magnets in the center hub pass the trigger coil creating voltage pulsesThese pulses turn on one of the two electronic switches (SCR) in the switch boxA positive voltage pulse turns on the SCR switch associated with cylinder #1; negative voltage pulse turns on the SCR switch associated with cylinder #2The SCR switch discharges the stored capacitor voltage into the primary side of the respective ignition coilThe ignition coil multiplies this voltage to value high enough to jump the spark plug gap 34000 volts for standard coils; 40000 volts for high energy coilsThis sequence occurs once per engine revolution for each cylinderSpark timing is changed (advancedretarded) by rotating the trigger coil on mechanically advanced models which changes the trigger coil position in relation to the magnets in the center hub of the flywheelSpark timing on electronically advanced models is controlled internally by the switch box with fixed triggerThe stop switch (or ignition switch) shorts the output of the stator to ground to stop the engine on all models