'98 VMAX 150 not picking up water

[aruba]

My VMAX 150 does not appear to be picking up water. No water is expelled from the motor and after a 90 seconds running, the overheat warning comes on.
Is this an impeller issue? Something else? How hard is it to replace yourself?

[CHRIS]

WHEN WAS THE LAST TIME THE WATER PUMP WAS CHANGED?