1968 Evinrude Big Twin, Big Twin Electric, Lark 40 HP Outboards Service Manual, Page 32Get this manual
DESCRIPTION MAGNETO The ignition system consists of flywheel type magneto connected to the spark plugs through high tension leadsThe magneto is se1f-contained electrical generating consisting of armature plate with two ignition coil and lamination assemblies, condensers, and breaker assembliespermanent magnet cast into the flywheel completes the assembly
THEORV OF OPERATION
The magneto employs the interaction of the fast moving flywheel magnet and stationary coil to generate electric current of voltage sufficient to arc across the spark plug air gapThis creates the spark that ignites the fuel in the cylinderEach ignition coil actually consists of two coilscalled the primary, consists of relatively few turns of hea vy gage copper wireThe other, called the secondary, consists of turns of fine gage wireThe coils are separated insulation and mounted the center leg of shaped laminated iron coreend of both the primary and secondary coils is grounded to the coreThe other end of the primary connects to the insulated stationary breaker pointThe other end of the secondary coil connects to the spark plugThe core and movable breaker point are grounded to the armature plate