Have a look here to see if you can find the specs you are looking for, http://www.boattest....rch_result.aspx.
Out on our test run the Utopia 185 ran at 45 mph at wide-open throttle, and her best cruise was 24.6 mph at 4000 rpm. At this speed the Utopia has a cruising range of 164 miles with a single fill of the 40-gallon fuel tank.
If my math is correct thats 6 gph.
164 total miles / 24.6 mph = 6.66 hours untill empty on the 40 gallon tank
40 / 6.66= 6.0 gph
From what I've read about on other boats I would doubt that 6.0 gph. 6 gph is really low for a v6 2 stroke outboard motor much less a jetboat.
"The Challenger 20' has 20 degrees of deadrise at the transom, which gives you the best ride possible in chop. We measured a quick hole-shot of 1.9 seconds to be exact. Its 2,100 lbs. is heavy enough for breaking through waves, but it doesn’t hold the boat back. In fact, this boat hit a top speed of 49.9 mph at 5650 rpm and her optimum cruise was at 27.6 mph at 4000 rpm. This all adds up to 109 miles of fun at best cruising speed."
109 total miles / 27.6mph = 3.9hrs
40gallon tank / 3.9hrs = 10 gph