so far this is what i have seen with the GT-150, 73 115hp Johnson no power trim, trim pin in second hole from transom.
Laurie and i in the boat, 9 to 12 gallons of gas in the bow.
1, unknown ss prop (with a few small nicks), 5600 RPM, 42 MPH GPS
2, 14x19P alum, 4900 RPM, 43 MPH GPS
3, 13x19P alum, 6500 RPM, 41 MPH GPS
these next 2 runs were Friday evening at rathbun, BUT... when i got home i found that the choke detent had fallen apart so that data may be skewed.
4, 13x21P alum, 4800 RPM, 44 MPH GPS
5, 12.75x21 alum, 4800 RPM, 44 MPH GPS
repeated run #5 with new plugs from Jerry same numbers. (orig BU8H, replaced with L77V)