Water pump not pumping

[Davie1961]

1978 6 hp evinrude.
I had no water coming out telltale or exhaust. Replaced water pump- still no water. Removed power head and head gasket and found no blockage. Found stuck thermostat and replaced. Reassembled. Tested water pump running lower unit in tank. It pumps. Reinstalled and still no water flow. All passages in lower unit are clear.
Any ideas?

 

[racerone]

Is water in your test tank / bucket 6 to 8" above the impeller ?

 

[Davie1961]

are you saying I need to have 6” of water above the water pump or the propeller? I might have that much above the prop.

 

[racerone]

Water needs to be 6 or 8" above the pump / impeller.----Get a bigger bucket and more water and test run.