Weird electric issue in old Johnson outboard
I have an old boat with a Johnson 120 on the back. It's worked faultlessly for years but recently developed a strange problem where it would sometimes start without warning when the key was in the 'on' position but I hadn't twisted it to start. I thought it might be something to do with the rusty battery terminals so took all the wiring off the battery and cleaned it. Now it does it all the time! Whenever the positive terminal touches the battery, the engine starts if the key is in the ignition. It seems that I've somehow shorted the key...
Is that right? Any ideas? I took the control box off and apart but everything looked ok inside.