Joel, I think you've gotten good advice from Steve. As the owner of fivel Cummins 5.9s ranging from 210 to 380 HP over the years, let me say that Steve Sipe's troubleshooting ideas ring very true to me. One additional thought I had: you might have a turbo issue. Sounds like you may not be getting any/enough turbo boost. What happens vis-a-vis the exhaust when the engine dies? If you're getting a big cloud of black or dark gray smoke, that would be further evidence of a malfunctioning (or non-functioning) turbo. In any case, take off the air cleaner and see if you can spin the turbo wheel. If not, you have your culprit. If so, look elsewhere. I've had a similar problem with my Cummins QSB on two occasions. But in my case the engine would run up to the point where the turbocharger normally kicked in but the RPMs would not go beyond that. In both cases, it turned out to be a turbo problem--one time the turbo was frozen and the other time it was a loose hose clamp in the air delivery system. With the electronic QSB the engine doesn't die if there's not enough turbocharged air for higher RPMs, the engine just won't increase RPMs beyond about 1600-1700 RPMs. But I've never experienced a shutdown like you describe. Good luck, Milt Baker, American Tug 34 Bluewater IV and Nordhavn 47 Bluewater