Marine Pumps

[Crackle]

I think it's an old water delivery pump. Brass type. It may work more slowly and cooled by the water.

It now sounds more like a rubber impeller type pump, not the centrifugal type commonly used for bilge pumps, driven by electric motor.
Is the pump similar to this. https://www.asap-supplies.com/pumps/engi...29500-1501
They often use that type mounted onto the marine engine to pump the sea water though the heat exchanger.
They are normally able to self prime from a couple of feet (so long as there are no air leaks on inlet), and can pump to a reasonable head.
If it is running hot and over current the impeller maybe jamming in the pump housing. When reassembling the impeller into the pump body I used Duckhams Keenol grease to help lubricate the rubber so did not burn before the water could cool and lubricate it.
Mike