If you are running off your main tank, I would be surprised if you can even monitor it. I have a 9.9 Yamaha and can troll all day and my gas gauge never moves. Compared to the main motor it's like having a hybrid, charges my batteries and runs on ounces, not gallons.
The one thing I would warn you is, the jets in these kickers are so small, they varnish and gum up very easily. I have eliminated this problem but running it out of fuel at the end of the day each time out, and by running non alcohol fuel. This is the second newer kicker I have owned and both have run smoother and idled better when I removed the cap and readjusted the idle mixture.