I cant seem to keep my motor running.At first I had a portable gas tank.It would run good about half throttle.As soon as I give it full throttle .it would start to die.Sometimes I could pump up the ball,about every 3 minutes,then it would start to collapse the ball,then die.I replaced the diaframs,but it did'nt make any difference.Then I put in a different tank in the front under the bow.Installed the proper vent,and new ball,new three eights fuel line.Then when I take it out,it will go full throttle for about 2 min.then die.It would start right up everytime.But it would'nt even run at half throttle for more than about 2 min.Then I put a low volume (6 to 8 psi ) electric fuel pump.I got the same results.Can someone please tell me whats wrong?: