1984-1986 Mercury Force 4HP Outboards Service Manual, Page 25Get this manual
SECTION
IGNITION
GENERAL
The Force H.Poutboard motor is equipped with breaker point magneto ign ition
OPERATION
Ignition Sy.m: The rotation of the generating magnets in the lIywheel creates rotating magnetic field which cuts through the windings of the coilgenerating voltageWh ile the ignition points are closed complete ci rcuit allows this current to fl ow through the primary coil winding building very slrong magnetic field in the secondary ind ing 01 the coilWhen the cam opens the STOP SWITCH- ,
ignition pointsthe magnetic field collapsesA very high voltage (approximately 18,000 volts) is induced in the secondary wind ing, and Is routed to the spark plug via the high tension lead When the Ign ition points are openself induced current flow In the coif is interrupted and the magnetic field surround ing the coil ind ings collapsesHigh voltage in the secondary winding goes to the spark plug