..."planing boats going slow only seem efficient compared to the prodigious fuel consumption when they're planing. "
Have to inset a caveat here: The gas mileage curve (0 to best cruising speed) is highest at around 4 to 6 mph, goes way down (bad) at 7 to 12 mph, then improves while on plane. My 32 footer gets its best on-plane gas mileage at about 14 mph (1.5 mpg). Above that the mileage slowly decreases up to where the secondaries open, then WHAMO!
Jeff
PS: I see boaters going along at half plane all the time, their boats 'climbing uphill' and wasting gas like crazy. No doubt their skippers--lacking a Flo Scan--think they're "saving gas".
"...reality is not nearly as lovely as the world of Liberal Land. No wonder so many people want to go there." - Tom Sowell