prop-17ss or 19m alum better fuel economy

[seapro21]

i have the right 2 props for my 2001 ox66 200 yam.the original - 19m aluminum. with that it tops out at 5000rpm.going to a solas 17x14 1/4 ss prop it tops out at 5500rpm which is reccomended.my question is which prop would get better fuel economy. i dont have a flow scan. with gas prices i am only running 4000rpm at about 23-25mph to save on fuel with the ss prop.wot i only get about 30-32 at 5500 so i am wasting the fuel at wot . i am not in any rush.if i put the 19m aluminum back on and still only run 4000rpm will my fuel economy get any better? the boat is a seapro 20001 21ft walkaround.thanks for any input

[boats.net]

If the SS prop will give you more MPH at 4000 rpm's than the alum then you may be able to cover more distance on same amount of fuel.