wannabe rs

hi all i am hoping someone can help i have a problem with the starter motor i have replaced it 3 times and all have blown i replaced the live wire as the old one had a bit of a burn and the rubber around the wire missing but now all it keeps doing is blowing the starter motors and i also get the battery light come up on the dash its now starting to cost a bit of money and i really want to get it fixed if anyone would know could they please advise me and the starter motor is on the back of the engine under the inlet manifold any help will be great cheers from karl