Electrical problem
1996 GMC Jimmy 6 cyl Four Wheel Drive Automatic 114000 miles

Positive battery cable wire from batt to starter, red hot sizzleing, removed old wire found a ground to the frame. Now, i replaced with autozone, may be 4gage wire, std off shelf, and same thing. sizzle hot, do i need a 2 gauge wire, or, what happens if I accidently reversed the neg/pos cables to batt. Before I removed old wire, the battery terminal silver connector completely melted and broke, apart, hence the new off the shelf pos cable. Also, new battery and when i disconnecte the terminal screw to let the wire cool down after 2-3 cranks, the bolt was very hot to the touch. HELP PLEASE..........Cmon doctors, how bout an idea.