Motor will not shut off

[Rare Air King]

I have a 1980 Mercury 1500. When I crunk it up for the first time (with the muffs) it did fine. I put it in the water and it will not shut off using the key. I have to unplug the fuel line every time. Pull it back on land and start it and it shuts off fine. Any ideas where to start?

 

[Chris1956]

Re: Motor will not shut off

If that motor has the six coil ignition system, the switchbox has a killer wire (orange) that is grounded by the ignition key to stop the motor. Check it with an ohmmeter.