i just installed a new fuel pump kit on a '68 6 hp and the pump worked perfect most of the day. But then when heading back to the dock the engine shut off. It's the same problem as before, the engine quits unless i keep pumping the primer bulb. I just installed a new gasket and diaphragm, but i didn't get the kit with check valves. Is this a problem with the primer bulb, or could something be wrong with the check valves? I just don't understand why it worked well then started having the same problem.