1994 Holden Rodeo battery boil over

Installed a bigger bosch alternator in my holden rodeo ute, it has a 4ze1 in it, think the alternator was out of a vr commodore, after installing the alternator I connected the 2 existing wires from the old wiring loom with the plug and the the B+ to the bolt on the back, I then connected the positive and negitive to the battery and it started boiling over straight away with the engine not running, it has never run in my ute as I just got it second hand from the wreckers, is it because it is to big for the engine or another problemwith the alternator please help me. Thx