I have a 50 hp Force outboard that runs good for the first five to ten minutes and then dies. It only dies at about half throttle or less. It runs fine if you keep it above half throttle and the rpm's higher. The minute that it starts to die you can pump the bulb and it will stay running for a few more minutes. Other than that it is getting annoying. Any help would be helpful. I have cleaned carb, checked battery, new plugs, and checked fuel screens in tank and pump.