Been there
Is it safe to assume you have a newport model Wilcox Critten? Think you will find you need a new impleller which has a slip clutch molded into its center which causes the impeller to operate when the motor spins in one direction but not the other. When the clutch goes the impeller doesn't spin in either direction, ie. not water coming in. It costs $60+ from the manufacturer for a new impeller. Be very careful doing the screws at the base of the unit, there are metal female sleves formed into the base which can strip out if over tightened, which means you need to buy a new base piece if this happens, oh yea $60+. I replace mind with a manual, I had enough.