The mid ’30s Evinrude/Elto coils I am familiar with have a primary voltage around 5 to 8 volts with a secondary around 40,000 volts. The secondary is a single winding with each end firing a sparkplug. Grounding one plug wire doubles the voltage to the other. One wire being disconnected also kills the ignition to the other sparkplug. Both wires must be grounded when cranking an engine with the sparkplugs removed.
Edit – The spark between the ends of the two high voltage wires should jump a 13mm gap
