Cant keep fuel pressure in primer ball

[bearsfan]

I have a 93 40hp Evinrude e40tletb when I pump the primer ball to start the motor the fuel will leak back out. Once I get the boat started the motor runs great until I turn it off and then the same problem I changed the ball and hoses but no change any idea

[boats.net]

Verify that you do not have any air leaks in the fuel system. Also, check your anti syphon valve.