The gears on my boat are the same as yours, m20 2:1. I'm sure some diameter has been lost with the couple polishings on the wheels, but not much. I usually carry full water but for local cruising I hold nothing in the rear tanks under the deck and only 100 or so gallons in the forward tank. I don't see any reason to sit on 500 gallons of fuel unless you're going to be using it soon. Another couple things I did was to remove the 45 degree or so brace on the aft most struts. I called SAMs and they explained that the brace was an attempt to get rid of some vibration but it was ineffectual. Also I saw how Viking was setting up the shape of their rudders to gain speed/loose drag so I copied that onto the huge hatteras rudder. It still turns on a dime though. So that smoothed out the bottom a bit. Another thing I did was to close up the holes through the hull into the live well. The bottom paint is relatively smooth with no peeling areas or huge texture. Any through hulls that weren't in use were removed. I don't really measure fuel burn. When the tank is low I add fuel! For long distance I would work with a figure of 40 gallons per hour at cruise speed. For the type of use the boat is currently asked to do it makes no sense to compute fuel burn numbers. If I was offshore fishing it would make perfect sense but I'm not doing that. You say your boat is light. Have you had it weighed? Once with full fuel and water, in the slings it weighed in at 37000 pounds. Exactly the quoted weight. I think the manufacturers assumes half load fuel and water though. I also don't have the gigantic raw water strainers for the engines. Only the outside screens. All unused wire runs were removed as well as old outdated equipment. Pounds add up quickly. Just ask any of the liveaboards that have boats that cannot plane due to all the possessions aboard. No offense, just the facts! You may be running up full rpm but maybe you're using all that horsepower to simply overcome a filthy bottom and running gear.
