I've been paying attention to my fuel consumption this season on my 23' MasterCraft 230 VRS with the NorthStar 5.7L LTR. Last season was the first year I had it and never checked.
We run anywhere from 580-1,600 lbs of ballast (Depending on who brings the bags) and 3-6 people in the boat. I've only taken it out about 3 times this year on quick after work trips where the engine gets about 2 hrs of runtime according to the tach (Supposedly accurate to 1/10th of an hr) and PerfectPass (~3 hrs "on the water" all wakeboarding, no cruising, minimal idling, no power turns).
I started filling it back up right after coming off of the water vs. running the tank down (60 gal) over the course of a few outings then refueling. Each time it has only taken about 9 gallons to refill the tank. I never trust that it's full with that little bit of gas despite what the fuel gage and the gas pump auto shutoff claims and end up overflowing it at least a couple of times to be sure.
Anyway, 4.5 GPH seems pretty low compared to what I've seen others post in other threads even for smaller boats.
FWIW this is with known ethanol free gas. I definitely need to get a larger sample size (more run time before refilling) to get a more accurate GPH number but is this impossibly low?