Can't start my 97 Murray

I can't start my 97 Murray 18hp 48" deck Briggs and Stratton motor listed as industrial. I've sanded down all connections to battery and solenoid. Battery is fully charged, tried jumping it and I'm getting just a light sound of it trying to turn. Other than that it's not even turning over or making any type of noise. Red wire from starter to solenoid it's not showing any bolts from other side of solenoid to battery it's reading 12.75 or there abouts. Is this the solenoid starter or ignition. Also I don't have a proper key for ignition since it broke.