Water Pump?

I just got this truck last weekend and the guy I got it from said that it needed a water pump, but just wanted some input from some mazda guys....The truck will start and run, after about 15-25 minutes it will overheat causing the water from the radiator to shoot into the overflow tube. I do not see any leaks or anything either. He claims 3 weeks ago he replaced the thermostat in it, and I have flushed out the radiator and put a new cap on the radiator also. Anyone have any input on what is going on?

Thanks,
Brad

OH jeeze not this again i had the same issue man and i ended up doing a motor swap.
its poss it could be the water pump but if your doing the water pump so the timing belt to dont use the old one
i ended upidoing a water pump .timing belt,rad,cap,then a head gasket,heater core i felt like i was chasing a ghost come to find out there was a small crack in the head.It was easier for me to do a motor swap since i had a low mile donar sitting in the yard anyways (plus i wanted to go from a auto to a 5 speed anyways) dont make the same mistake i did and chase ghosts if the water pump dont solve your problem think about a clogged line or something else but it sounds to me like (sorry to say it) from past experiance (head gasket)GET THE HEAD MILLED AND PRESSURE CHECKED.

Alright bro, thanks for the input...I've already picked up the water pump, timing belt, cam/crankshaft seals....I don't really care what the problem is, I just want a truck that runs! I also have a B2000 motor if all else fails i could throw in it? I'm not sure how it runs though, was told it was good running condition.

Sounds like the thermostat is stuck closed if its boiling over after 15 mins. Try running it without the thermostat just to see if it still overheats.

Yeah it still over heats with the thermostat out man, now im thinking about doing a motor swap....

Its more then likly a head gasket. and pulling the thermastat is one of the worst things you can do it doesnt slow the water down in the radiator long enought to cool it down. if you open your overflow and it smells like exhaust fumes then it is a head gasket for sure. if the water pump is bad it will leak out of the weep hole. and if the thermastat is stuck close it wont boil over for the fact that water is not moving though the system. but the temp gauge will read hot.