Mercury 150 Fuel Mileage - 1971 20' SF

[plusone876]

I have seen 41mph on my gps (I think the tide was flying out and the wind was to my back). Usually my max is around 38-40mph though. Should I see better fuel economy and speed with a three blade prop? I know the four blade prop has a better hole shot and increases stern lift. I have one as a spare, just never used it.