1977 Johnson 2HP Outboards Service Manual, Page 28Get this manual
BREAKER ARM
MAGNETO The ignition system consists of flywheel type magneto connected to the spark plug through high tension leadThe magneto is selfcontained electrical generating unit consisting of an armature plate with one coil and lamination assembly, condenser, and breaker permanent magnet cast into the flywheel completes the assembly45147
THEORY OF
The magneto employs the interaction of the fast moving f1ywheel magnet and stationary to generate an electric current of voltage sufficient to across the spark plug air gapThis creates the spark that ignites the fuel in the cylinderThe ignition actual1y consists of two coilscal1ed the primary, consists of relatively few turns of heavy gage wireThe other, cal1ed the secondary, consists of turns of fine gage wireThe coils separated insulation and mounted the center leg of shaped laminated iron One end of both the primary and secondary coils is grounded to the The other end of the primary connects to the insulated stationary breaker pointThe other end of the secondary connects to the spark plugThe and movable breaker point grounded to the armature plateWhen the poles of the f1ywheel magnet sweep past the first and center legs of the magnetic f10w is momentarily established in the The temporarily assumes direction through the from the north pole of the permanent magnet to its south poleAs the poles of the magnet sweep further along the in the center leg col1apsesThe rapid development and col1apse of in the center leg induces electric charge in the coilsThe current in the primary f10ws through the closed breaker points and sets magnetic of its own in the center leg of the The direction of the mentarily opposes the establishment of reverse in the center leg as the poles of the f1ywheel magnet reach to the center and third leg of the At this precise moment, the breaker points opened the engine crankshaftThis interrupts the f10w of current in the primary, and the opposed in the center leg col1apses