When I head out in our 2120 the boat is generally loaded with two big people, 36 gallon bait tank, full fuel tank, lots of ice and plenty of gear, so it's pretty well loaded down. In decent seas I find 3700 to 4200 rpm to get me between 18 and 22 mph which I like as a cruising speed. Based on GPS miles traveled and topping off the tank after trips the math works out to between 2.8 and 3.2 mpg.