My unit will falter after running 15 minutes

Terry you may want to clean out your gas tank as there may be some dirt blocking the fuel line in the tank . it may also have something lodged in the fuel line so use compressed air to blow backward up the fuel line to the tank. Also some ethanol based fuels can cause a green slim to form in a tank that has sat for a while and this slim can plug fuel lines and filters. The plugged line may be letting some fuel through just not enough. There could also be blockage in the carb itself at the needles to properly clean them you will need to remove them . Carb cleaner wont help there, remember to count the turns from bottom to be able to reinstall them . Hope this helps