So I'm a rookie, but reading alot, and trying to learn. Cummins 6BTA, 400 hours, recon 2007. You guys helped me out when I posted 2 weeks ago about OVERHEATing. Since overheating a lot has been done. Hired a Cummins/boat mechanic. Raw water system serviced: flushed, barnacle buster, strainers checked, impellar changed, coolant changed, hoses changed. Alarm working fine. Tach checked, propped close to ok; engine rated at 3000 rpm, turning 3060. Here's my new dilemma. Running at 2100 RPM, and engine stalled. Two 120 gallon fuel tanks, each half full at start of trip; by dipstick. Fuel filter had been changed. Somehow air got into the fuel lines. I primed the lines and was able to restart engine. ran fine for a while, but then stalled again. Reprimed, fine. Checked fuel tanks; starboard tank almost full, port tank 1/8 full. Shut port tank valves off, and ran fine into dock. Help.