1974 40hp Merc won't shut off

[dfrants]

picked up a 1974 40hp Merc. that starts right up but doesn't want to turn off. it will almost kill when you first turn off the key but struggle and kept running. the wires under the hood are pretty bad. which color wire controls the off position on the key?

 

[Chinewalker]

Best to just go through and rewire the whole thing. Last thing you need is something arcing out and starting a motor fire or leaving you stranded. Or both. Those older Mercs are notorious for badly aged wiring. To answer your question, the brown wire is the ignition off wire.