Harley Gas to Electric Help!

[OneTuscani]

I recently purchased a older Harley Davidson 3 Wheel golf cart for 50 bucks. I was gas but was switched to Electric. The Electric motor says its Amd/Harley so Im assuming they just took the electric motor out of another electric Harley model. Anyways I know nothing about electric engines or anything.3 batteries are 3 years old(Interstate 6v) and 3 were bought last year(Trojen T-105) The guy I bought this from said it worked great till he put the new batteries in and he is a little odd. Well I got to looking and there are some batteries that go + to - and some that go - to +? What is the proper way to hook Six-6v batteries up to get 36v? I am getting a volt meter tomorrow to test all the batteries and silonoids, but the batteries just dont look right hooked up the way they are. Also there was so much corrosion on the cables I'm thinking I just got a good deal after I clean all the cables. It holds a charge for about 1/2 mile and then its done. Also 1 of the ground cables was not connected!