On my 1976 evinrude 40hp there is no cooling water coming from the leg. I have fitted a impeller to correct way, put a hose pipe on the water tube and water flows around the engine and out. The intake is clear. When it runs only a trickle of water comes out? No idea why this is. The water tube is correctly installed into the impeller housing and the wooddruff key is engaging.
If the water circulates through the block by putting a hose on the water tube, I would submerge the lower unit in a barrel of water and spin the drive shaft and see if the pump shoots water out of the output.
Did you spin it clockwise?
The best is to put it with water level above the pump and a piece of plastic tube/hose or whatever in the pump-outlet.
Just watch out so you do not drown your power drill!!!!
A couple of ways:
1: If you have a socket that fits on the spline, then a bolt in the square of the socket.
2: Clamp a solid rubber hose on the shaft, a bolt inside the hose on top that fits into yous chuck.