snapped water pump

[lilhachithatcould]

Okay, here's the deal. my boyfriend has a '84 sr5 w/ a 3 tc. He recently replaced the water pump twice. Both times when the car was revved hard it snapped the front of the water pump. The first water pump had thinner metal and the second was thicker but both snapped liked twigs when revved hard (like 6,000 rpms) Like the whole front metal piece gives way. He changed the fan out to a different fan. It's not electric. but he keeps having to change the water pump because it snaps. He only tightens it down by hand and it doesn't seem too tight. His alternator is starting to fail. it's overcharging the battery. He thinks that the problem could be caused by the pulley attached to the water pump is bent or possibly the fan is bent/ not running straight. Neither of us can figure out exactly why it keeps doing this. Any ideas on what could be causing this???