I have a 2005 merc 50hp efi outboard on a 22' pontoon. The motor is running out of gas while going slow or WOT. I have changed the check valve on the tank, new OEM gas line and bulb, fuel/water seperator,and checked the gas pickup for cracks. Still does the same thing. While I was winterizing the boat I noticed the motor would start to tick slightly before it would starve for gas. Sort of like a valvetrain tick. But if I squeeze the primer bulb slightly the noise goes away. Fuel pump?? Can you rebuild them? Also there is a small screw at the bottom of the pump. Is that a drain screw for the pump? It has never been removed or drained since I owned the boat. Could this be part of my problem? Any help would be appreciated. Thank, Mark