The 5.4 mpg was with the bimini top down, and just two people. Loaded with 6 adults, it planes in about 6-7 seconds, and has a WOT of only 30 mph, cruises at 22-23, but the rpms jump by 200 to hold that.
My prop is wrong pitch to run fully loaded. Max rpm with just me is 5200, max with 6 adults is only 4850. Recommended range is 5000 - 5750. My opinion on propping is that I should be able to turn Max of Max at Max for safety reasons. That means I should be able to turn the max 5750 of the maximum rpm range with the boat loaded at maximum weight. So with full fuel and 9 people in the boat, I want to be able to turn 5750 rpms at optimum trim.
I need a different prop, but haven't found the right one. I currently run a Trophy Plus SS 4-blade 13.25"Dx21"P. I need to drop that at least to an 18"P, but my local dealer hasn't got one, and since I've had this prop over a year, won't trade me for a new one, but offered me $250 in trade toward one ($650). I've had this prop over a year because he told me just to hang on to it and he'd trade when he got an 18" or 19" in stock.
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Common Sense is learning from your mistakes. Wisdom is learning from the other guy's mistakes.
Fr. Frank says:
Jesus liked fishing, too. He even walked on water to get to the boat!
Currently without a SeaCraft 
(2) Pompano 12' fishing kayaks
'73 Cobia 18' prototype "Casting Skiff", 70hp Mercury