It’s true they like to drink fuel but if you really take time and trim the boat for the sea conditions you can get 1.2 mpg but it takes practice. I’m mainly interested if anyone has continued problems other than the flywheels.
I bought a 2011 Freedom 275 with an F350 on it recently. At 750 hours, the engine passed a mechanical inspection and compression test fine with ~5% variation between the highest and lowest readings (a healthy engine has 10% or less variation). It hasn't given me any trouble.
The factory performance test for a 275 with a single 350 appears below.
My experience with a hardtop and isinglass is:
5700 rpm - 33.3 gph - 45.0 mph - 1.4 mpg (WOT)
4900 rpm - 20.4 gph - 37.4 mph - 1.8 mpg
4300 rpm - 14.3 gph - 31.8 mph - 2.2 mpg (cruise, for me)
I cruise at 4300 rpm to stay just above the range where flywheel degradation happens even though 3700 would be better from an efficiency perspective. Fuel consumption climbs noticeably above 4000 RPM and then it really ramps up above 5000 RPM. The nice thing is that these torquey engines can be run at a slower RPM than V6 competitors.
Of course you will burn more fuel pushing a 305.