Here's a general comparison...from our beach.
1-Basically stock 09, 701 SJ with a limited "B" pipe, dual 38mm's.
2- 2, FX-1's, 61X,701,(wet jet intake,single 46mm)with sport port, "FX B" pipes, & 140mm kawi pump mods.
3- FX-1, 827 (865) dual 46's, epic ignition, 144mm mag pump.
4- Square nose SJ, 61X, limited "B" pipe, group k porting, impeller, grate, & bumped compression.
All of the boats have SJ 4.8gal fuel tanks. We all fill up, and go for a ride. The run times are identical, the 61X engines consume more fuel on the average ride (they hit reserve first). Back at the truck, the stock SJ ends up consuming just a few ounces less than the 865. Our rides our limited to fuel, sometimes there is 1/2 gallon or less when we return.
I've never messed with the SBN 38's, they might work out to save a little fuel in the long run.
But a 20min putt... putt.... slow, no wake zone? That's a rhythm breaker for sure.