I have a 2012 Ankona Copperhead with a 60 E-tec and a 12 gallon tank. My gas gauge is the Evinrude Icommand system and displays digital. When I refill the boat I always reset it to a full 12 gallons. Last night I ran out of gas with "4.4 gallons left" on my gauge. I can see being off by a gallon or maybe even two, but 4? What's the problem with it? How can I fix it? Any input will be helpful. Thanks