Starter

Was it a re-manufactured starter? If so take it back for another one or a brand new one and/or make sure it was connected correctly and no bare wires touching each other. Check positions of all wires by the starter. May be one of your wires is touching something it shouldn't. Pay attention to proper routing of the positive (+) battery cable where it bolts up to the starter too.

More than likely the small wire on the starter solenoid is touching the positive post or the main cable is hooked onto the bottom post. Check the wiring on the solenoid as enginecreator suggest.