Overheating when boost hits

[bluecoot]

My buddy has a 2002 7.3 psd. He has replaced the motor with a new one. It startes up good and idles perfect, but when you get into the pedal and start to built boost it overheats. Anything you guys have will be great. Thanks
Matt

 

[Brianedwardss]

Could simply be a bad or upside-down thermostat in the new motor.