I have a 95 60 hp Mercury on a Tracker V-17. When my 18 gallon gas tank gets appx 1/2 empty my motor will stall on fast acceleration. Sometimes I can baby the throttle and it will get up to full speed - but sometimes it just wont run but about 1/4 throttle. It doesn't do this if my tank is full. Is it trash in carb or possible fuel tank/line problem?????