During my last brew, my March pump couldn't lift the water to my HLT. I moved the water manually, then disassembled the pump while I heated the sparge water. After one years use without disassembly the March pump cavity and impeller were spotless. The stainless steel impeller shaft needed to be cleaned up with 600 grit emery paper. Brew day saved! Love my March pump. It is a geat product!

Did you find out what the issue was? Bad prime? What is your oiling schedule for the motor?

The stainless steel fixed shaft that is part of the internal pump housing, that the impeller spins on, had some minor crud build up on it that didn't allow the impeller to spin freely. Once I cleaned the shaft with 600 grit paper, reinstalled the impeller, and reassembled the pump. It pumped great. The motor speed was always normal because it is a magnetic drive. I noticed the problem when I couldn't pump water vertically 4 feet to my HLT. It is easy & quick to dissasemble. A nice design!

The sugars in the wort and the heat will cause the sugars to 'plate' onto the impeller shaft. I use a March 809HS for my RIMS. Once I start mashing, I never turn off the pump motor. When I'm moving hoses or other actions, I just shut the output valve and leave the pump spinning. If I don't do that, sometimes the plated sugars make it impossible for the motor to restart the pump.

A hot recirculation of PBW solution after brewing does take care of the plated sugar on the shaft.