74 Mercury 1500 Ignition Switch wiring

[SanAntonioDad]

Howdy folks. The person who owned my boat before me replaced the factory Keyes ignition switch with an aftermarket. The harness is the factory harness with salmon, yellow, white, brown, black, white, and red. The ignition switch has 6 poles. They are B, M, M, S, I, and A. Does anyone have a diagram for this type of switch or know where the wires go. The wires were so corroded inside the mercontrol, they all broke off when I was removing it. Can't tell for nothing which went where

 

[SanAntonioDad]

Sorry, that should have been, "factory keyed ignition switch." Dang spell check.

 

[mrmotts]

No Title

Here's the original wiring. Turning the key while checking terminals with a multimeter should tell you how to match up the old wires with the right terminals. I would also check the wires inside the original harness with the multimeter, as they may be corroded somewhere along the line, the insulation wasn't the greatest back then.

 

[SanAntonioDad]

Awesome! Thank you very much for the help. I managed to find a used harness that checks out well with the ohm meter. Just wasn't sure where to connect them to.

 

[Chris1956]

SA Dad, Your motor needs to provide +12VDC to the switchbox to have spark. The salmon wire may be connected to the M terminal, but is unused. The white wire supplies voltage to the switchbox, Connect it to the I terminal.

So Red to the B terminal, Yellow to the S terminal, Black to the M terminal,


Do you still have a working choke button? It gets the grey wire. Brown wire is tach sender.

 

[SanAntonioDad]

Chris1956,
Thank you very much. It doesn't look like the choke button was ever wired. The button is bad, and there wasn't any sign that anything was connected to it. Someone also removed the neutral safety switch :-/

 

[Chris1956]

You really need a choke to cold start that motor. Any kind of button will do, but the original button in the MerControl was pretty robust. See if it can be reconnected. Maybe whoever removed the neutral safety switch (also in the MerControl) also cut the wires to the choke button?

 

[SanAntonioDad]

That's what I'm thinking too. I've read quite a bit in this forum about how hard to start these are when cold. Thanks for the help.