Water Pump Carnage

[guntherrex]

cavitation is often the cause of serious impellor damage, however it is often and the end of the blades and not the middle. There's not enough detail in the picture to assess that, you should be abe to see a porous surface at leading edges or inside corners where the vacuum bubbles impode and chip away the material.

in this case a bad fit in the pump housing and/or debis between impellor and housing seems possible too