Yamaha G9 Golf Cart Engine Won't Stop Running

My Yamaha G9 golf cart engine won't stop running. I can hook up the battery turn the key on and when I step on the gas pedal the engine starts as normal. But when I let off gas pedal the engine stays running. I can not shift into reverse. I pulled the spark plug wire and the golf cart still stays running. I had to pull battery cable off to shut off the engine.
Yes. I had the battery out and power washed everything. My son told me he put the battery back in and turned the key on and a wire started to smoke. He fixed the wire (spliced a new wire in) and that is when the problem started. The wire was brown in color. I think he may have hooked the battery up wrong? If so what would this do?