Purchased a 98 Back Country flats boat with a 1996 Mariner 135 Serial# 0G 384616. When the boat was purchased the previous owner was running the boat on a 12gal. external/portable fuel tank, boat ran fine. I removed the portable fuel tank and reconnected the fuel line to the original fuel tank on the boat. The boat will start and run after priming the bulb but runs out of fuel. Where should I start my trouble shooting.