Re: 1997 9.9 Merc 2 stroke, no spark either cyllinder
This is a general description of the system
The ignition system is an alternator driven capacitor discharge system. Major components
of the ignition system are the flywheel, stator, trigger coil, switch box, 2 ignition coils and 2
spark plugs.
The flywheel has permanent magnets mounted in both the outer rim and the center hub.
The BLACK stator assembly is mounted below the flywheel and has a low speed (LS) and
a high speed (HS) capacitor charging coil. Low speed coil provides primary voltage to the
switch box from idle to approximately 2500 RPM. The high speed coil provides primary voltage
from 2000 RPM to the maximum RPM the outboard is capable of achieving.
The RED stator assembly is mounted below the flywheel and has only one capacitor charging
coil.
As the flywheel rotates, the magnets mounted in the flywheel outer rim pass the charging
coils creating voltage. This voltage is rectified to DC and charges the capacitor located in
the switch box.
As the flywheel continues to rotate, the magnets in the center hub pass the trigger coil creating
voltage pulses. These pulses turn on one of the two electronic switches (SCR) in the
switch box. A positive voltage pulse turns on the SCR switch associated with cylinder #1;
a negative voltage pulse turns on the SCR switch associated with cylinder #2.
The SCR switch discharges the stored capacitor voltage into the primary side of the respective
ignition coil. The ignition coil multiplies this voltage to a value high enough to jump the
spark plug gap ? 34000 volts for standard coils; 40000 volts for high energy coils.
This sequence occurs once per engine revolution for each cylinder.
Spark timing is changed (advanced/retarded) 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 flywheel.
Spark timing on electronically advanced models is controlled internally by the switch box
with a fixed trigger.
The stop switch (or ignition switch) shorts the output of the stator to ground to stop the engine
on all models.
