Fuel Economy Anyone?

This boat is teaching me a lot about boat design. At normal cruise we burn about 2GPH. The boat has no stern wake. That's right, no stern wake. This is in a displacement boat which is the key, I believe, to good fuel economy. Last weekend we ran 1550 to 1600 RPM most of the time and averaged 7+ kts burning 1.7 to 1.8 GPH. The boat is "happy" at this speed and I think for the 48 this is the "sweet" spot. Running harder gives us little gain for a lot higher fuel burn.