I have a 2005 60 hp mercury 4 stroke that is giving out of gas when running at 3/4 to full throttle. It will shut off and I will pump the bulb a few times and crank up and go again for 1 to 2 minutes and it does it again. What could be the problem. I did replace the bulb and the gas line with no change. This motor is in a 2005 Bass Tracker with a 21 gallon gas tank. Thanks in advance.