I have a 2012 Ranger 521 with a 2018 Mercury 250proxs 2 stroke. When I idle for long periods of time the motor goes dead and the primer bulb will be empty. It isn’t sucked flat just full of air. It was doing it after about 5 minutes of idling and I replaced the primer and now it will idle for about 15 min but still runs out of gas. I have replaced the fuel lines from the tanks all the way to the motor. I checked the fittings coming out of the tank and there aren’t any antisyphon valves. Does anyone know what I need to check next?