I have a 32 Open with Volvo 310 HP. Great boat. Not a speed demon but great on fuel. Trolling for walleye needs one engine in gear (2mph)with autopilot working to keep heading. I don't have trolling valves. But puts me at .25 gal/hr...nothing. Cruising is 11-13gal/hr per side @ 25-28 mph. Cummins should be very similar.