1984-1986 Mercury Force 9.9 and 15HP Outboards Service Manual, Page 26Get this manual
SECTION
ELECTRICAL SYSTEM
OPERATION
Magneto IgnilionRotation of the generating magnets in the lIywheel reates rotating magnetic field which cuts through the primary windings of the coilgenerating voltageWhile the ignition points are closed complete circuit allows this urrent to low through the primary coil winding building very str ong magnetic fie ld in the secondary winding the coil When the cam opens the ign ition points, the magnetic field col lapsesA very high voltage (approximately 18,000 volts) is induced in the secondary windingand is rouled to the spark plug via the high tension lead When the points