I have the same boat.
I have a Navman fuel flow meter on my boat and burn around 14gph at 4400RPM's.
Depending on load and sea state that can mean different boat speeds. In flat calm seas and a light load I can see 28mph at that speed, but in heavy seas and loaded down that can drop to 20mph.
Using the worst case scenario and about 1.3 mpg, the boat has a theoretical range of 1.3 x 173 or about 225 miles. Again, that is worst case. I know in reality I get much better.
On a couple offshore trips sharking, I've got as good as 1.7mpg.