I have a two stroke Johnson 115hp. I can squeeze the primer bulb till it is hard and the engine will run until it depletes the fuel in the bulb then stalls. This only happens at low trolling speeds. If I throw the throttle and run it at full speed, I have no problem. Drop back down to a low speed and it will stall as soon as the gas is depleted from the bulb. I replaced the bulb and the issue has not changed. I replaced all of the fuel lines last year. I checked all of the connections and all seem good. Boat has a built in 18gal fuel tank. Could it be a fuel pump problem and any idea where it might be located. Any ideas as to what I am dealing with or should be looking for would be greatly appreciated.