The water in the motor now has 'hydro locked' the motor - boat will need plug pulled and inverted and tilted several times to make sure water is out of engine and exhaust
Hooked up wrong or faulty pump
Pumps have a vacuum side and a water side - if you hook vacuum line to water it will fill motor with water (like it sounds like it has done)
If gasket between two side of pump has failed it will do the same - too much hose water pressure of faulty gasket
Clean it out and check hook up of lines - look at pump - water one side - vacuum the other
Later