I don’t believe a 4425 has a water tube as such. It is a passage cast integrally in the swivel tube and pump housing. I am posting a picture which I am quite aware is NOT your model, but attempting to explain how the water gets to the powerhead. This one does have a short copper tube leading to the cast-in tube (ignore it).
As for your motor, are you running it in a tub? If so, try running it with the propeller removed. Centrifugal pumps balk at working in turbulent water (tubs & barrels). Another thing to check is for a missing welch plug above the pump.
