For what it is worth. Having my grumpy old man moment. I used a Flo-scan for a number of years on my first 22'. And what did it tell me that was really important and useful? Hmmmm. Well, it told me that so much gas ran through it and approximate MPG when GPS distance over water was factored in. It also told me that I had one somewhat inefficient motor and hull drag because everyone else with the same motor and hull seemed to get better overall performance (according to their reports) Too humbling for me not to match up. So one day I jerked out the hoses and wiring and apparatus, sold it, and checked the tanks periodically for their level. I figured that it was just something else to go wrong, leak, etc. and I don't miss it all.
But if knowing that current, tide, and wind, plus elevation, load and boat handling are variables that can affect your fuel efficiency, by all means install a Flo-Scan so you can determine which variable it is that makes a difference. Actually, the translucent gas tanks (which show up very nicely at night time with a flashlight) are all I need for checking fuel consumption. End of grumpy old man moment. Yellowstone