I have a 1994 yamaha 200 hp, bilt in tank 100 galons. With Full tank go out . Less then 1/3 of tank empty ( 3 hours troling at 10 mph)all of a sudden sound like it was about to die . I squeeze the primer bulb and runs perfect , after a few minutes primer bulb goes flat. I star checking the fuel sistem desconecting the primer bulb , pumping again and runs for minutes. Replaced fuel pumps ,primer bulbs,filter, fuel lines, tank vent for blockages . Still the same. Please Help Me