3 blade 21 pitch was a bust, bad slipping (motor is a little high) and bad numbers.
bought a new merc revolution 4 blade 19 pitch and reproduced same numbers as the test, 4000 RPM gave 29.5 mph and 8 gph. When I was out of the wind, it was actually below 8 gph
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I confirmed the fuel flow meter is accurate, filled it up, ran it, said 17.8 gallon burned. Took 17.9 gallons when I filled her up. I think at dead idle the flow is too slow to measure and that accounts for the .5 % inaccuracy, or maybe it was warmer when I filled up and gas expansion accounts for it
I super happy with this: over 3.5 mile per gallon. Now if the wind would just let up I can take her fishing again