By impeller pump do you mean a centrifugal pump? Jabsco
uses the term "impeller pump" to mean a soft impeller vane pump, as in the Youtube I posted. They are positive displacement
, self priming, and can be quickly destroyed by being run dry. They are common in raw water
supply for cooling
. Centrifugal pumps are not self priming or positive displacement, can be run dry, and are common to bilge
There are also vane pumps, with rigid vanes that slide in slots in the hub. I'm familiar with them as priming pumps on a fire engine
, but have not run across one on a boat
calls an impeller pump could also be called a "soft vane pump," I guess.
Damned confusing for after only one cup of coffee.