How to Wire a Johnson Ignition Switch (2024)

When you look at the back of the ignition switch, you see six terminals, five of them around the outside of the back of the switch and one in the center. The terminals, clockwise from the "B" terminal are labeled "M," "S," "A" and a second "M." The terminal in the center is marked with the letter "C." If you find yourself intimidated by the handful of wires that need to go onto the correct terminals, relax. The solution this puzzle is as easy as looking at the face of a clock.

Items you will need

• Small adjustable wrench

Disconnect both cables from your boat's battery before beginning the work. Note that the nut on the positive battery terminal that holds the red cable, is marked with a plus sign or the letters "Pos." Removal of the nut on the positive terminal requires a 3/8-inch wrench, while the nut on the negative terminal, that holds the black cable leading to the boat's common ground, requires a 5/16-inch wrench.

Locate the "B" terminal at the 12 o'clock position on the back of the switch. Move to the 2 o'clock position and find the "M" terminal.

Loosen the "M" terminal nut with a small adjustable wrench. Slide the spade connector of the black and yellow wire under the nut until the connector is fully engaged. Tighten the nut.

Continue clockwise from the "M" terminal, until you reach the "S" terminal, at the 4 o'clock position on the back of the starter switch. Loosen the terminal nut and slide the spade connector of the yellow and purple wire under the nut until it stops. Tighten the nut.

Advance to the 8 o'clock position on the ignition switch's rear panel, where you will find the "A" terminal. Loosen the nut and slip the spade connector of the solid purple wire beneath it. Tighten the nut.

Go clockwise again, to the second "M" terminal. Loosen the nut, as you have with the other terminals, and slide the spade connector of the black wire underneath it. Tighten the "M" terminal nut, move to the "B" terminal and loosen its nut.

Slide the spade connector of the pink and purple wire under the "B" terminal nut and tighten it. Move to the second "M" terminal, loosen the nut and slide the spade connector of the black and yellow wire beneath it. Tighten the nut and move to the "C" connector in the center of the switch.

Unscrew the nut on the "C" connector enough to slide the spade connector of the purple and white wire under it. Tighten the nut. Reconnect the battery cables.

• When you're working on your motor, disconnect the battery cable from the negative post of the battery by removing the nut from the battery post and lifting the cable from the post. Removing the negative battery cable isolates the electrical circuit from the boat's common ground, making it "electrically safe" to work on the boat's electrical or mechanical systems.

• Pull the wiring harness up through the hole in your dash before you mount the ignition switch in your dashboard. This allows you to make the connections in relative comfort, rather than undergoing the near-impossible contortions required to get underneath the dash to wire the switch after you have installed it in your dash.