This season I dumped my old Polaris for a Dolphin Nautilus, I'm happy with the decision. I tossed the old rickety Polaris bot but kept the 3/4 HP booster pump, thinking it could possibly be used as a pool drainage pump. I rewired it for 115Vac and gave it a try tonight, just would not prime. I put the inlet hose up to a pool return forcing water into the pump...it finally started pumping. The second I removed the inlet hose from the return and dropped it in the pool, the water flow stopped.
The booster pump sure worked well when it was being forced water from my main filter pump in the original Polaris setup. I guess this type of pump can't self prime and continue moving water unless it is pressure fed?