"6 gallons in two hours - or t
"6 gallons in two hours - or to put it another way, 3 gallons per hour with a 100 horse - that's outstanding if the speed was anything above a fast troll.
As to tank size, depends what you use it for. I run my 140 off a pair of 40 gallon tanks, and that could be considered a little bit "undertanked" - ya, 80 gallons is kinda low for a 140 which can "guzzle" about 14/15 gallons per hour if I open her right up - which would give me less than 6 hours of run time, wide open.
At cruise speed, burning about 6 gallons per hour @ 22 mph that gives me a little over 12 hours on the water before the tanks are dry - or an average weekend out...
If you burned 6 gallons in 2 hours "doing what you normally do with the boat" I would consider "at minimum" a 24 gallon tank which would give you a complete day on the water (8 hours worth of run time)..."