I have a 1969 crestliner Norseman. I believe it has a 120 4 stroke mercruiser. My battery has been constently draining so I narrowed it down to the main red power line that starts the boat. Even when I have the key off, when I touch the line to the battery it sparks. I dont think it is the key for when I turn the key on and push the START BUTTON it starts. to turn off, I turn the key to off and it shuts off. Why is it pulling? HELP PLEASE! Thanks!!!!