1972 Johnson 100 HP 100ESL72R

[Mattamuskeet]

I just acquired a 1972 Johnson 100 HP (100ESL72R) that needs new spark plug wires. The old wires were unscrewed from the distributor cap assembly. I have made up new copper core wires, but do not know the order to attach them to the distributor. When I try to start the engine, it backfires, so I assume they are not connected to right ports. The picture of the distributor cap assembly in all of the parts diagrams I have found online shows four ports for screwing in the wires. However, there are five wires. Four are spark plug wires and the fifth is for the coil wire. The cylinders have numbers stamped on them but there are no numbers on the distributor ports.

Will someone please tell me the corresponding ports on the distributor and the firing order for this motor?