Merc 7.5 starving for fuel

[erichy]

Hi guys I'm a newbie to boats and have a question about my kicker motor. I put a 7.5 Merc on my Wellcraft 196 and it won't pull fuel from the tank if the fuel line comes from above the fuel hookup.When in the water and the tank is in the boat the line goes over the transom and to the motor, the tank is about even with the fuel hookup. It won't pressurize the ball when its in the boat. When I'm in the driveway and the tank is on the ground below the motor there's no problem, it pressurizes the ball and runs fine. The tank is a plastic Walmart cheapie that was given to me and the line and ball are brand new. Is it the tank or does the line need to be below the hookup to work? I figured it's a pressurized system so it wouldn't matter but like I said I'm a rookie.