Was fishing fine and started motor many times. The last time It didnt crank right away but something kept running. Sound like a humming sound. Kill switch didnt stop it, only way to stop it was to unhook the battery. Checked the ignition switch and unplugged the red cable and still the engine would attempt to start if i touched the wires to the battery. Finally after using the trolling motor to get back to the ramp, I took off the red cable from the starter. then I was able to put the wires back on the battery so I could trim the motor. I put the red wire back on the starter and it stopped. I have put a new starter on the engine. this was the first time out. I had started the boat 5 times earlier in the day with no issues. Any ideas??