I have 1993 larson with a mercruiser 4.3lx/v6 thunderbolt iv igition. I took it out saturday and my coil went out. Replaced coil that night and the boat started right up. Went out sunday. Ran good for about 5hrs, then it quit again. Replaced coil again and it fired right up. Don't know why the coil kepts going out. Also on top the motor I have a black wire( looks like ground) thats not connnected and a purple wire. Need wire diagram. Thanks