bronco dies out

I have a 1994 bronco. the positive battery cable is fried, so if i want to start it, i have to jump it. when i do, i can have my bronco running for hours in park. as soon as i put it in drive and i attempt to drive off, the engine dies out. what could this problem be?

Alternator? Have you replaced it yet? I replaced the one on my 88 about 4 years ago. It was fine after.