I have been looking into decreasing my fuel burn. Besides extra weight, props have the largest impact. I am running 17 on twin yamaha 250 OX66. Did switching to a four blade props make a substantial deference?? What are others running on there boats?? I think Grady recommends 19?? Looking to get 1.2 or 1.3 mpg if possible on the other hand with gas at 2 dollars a gallon not as critical to be worried .2 or.3 mpg.