Georgs, I don't know where the figures come from, but they are within 10%. With CPPs, to get the best fuel economy one must play around with the pitch, rpm and this is in relation to the wind, seas, load and other factors. In the end you get it close on short trips and let it go. On long trip when you are just sitting there anyway you have all day to play and see how good you can get it. For someone who likes to play with power transmission they are the ultimate toy. While you are doing this you must watch you exhaust temp so you don't overload the engines. Dennis