For my purposes...I threw out the 4 stroker answers (since I have a 2 stroke and they burn more)
Out of the replies
4 had 6 gallon tanks with engines that ranged 9.9 hp to 65 hp
3 had 12 gallon tanks with engines that ranged from 25 hp to 60 hp
1 had a 9 gallon tank??? with a 60 hp 2 cycle engine.
I looked up the measurements on the 6 and 12-gallon tanks from Atwood. The 12 is a few inches longer than the 6. That few inches will probably determine my answer.
If I can squeeze the 12 in, I might as well have it...since I am changing tanks at this time. If it won't fit, it won't fit...and I'll use the new 6 and figure out a way to carry two or three gallons in reserve.
I've seen references about some guys buying the premixed gasoline in metal cans at Wal-Mart ( or wherever). After they use up the premix, they just re-fill the one-gallon bottle/cans and keep a few in the boat.
Anyone do anything like that? I don't think I have room for a second real gas tank.
I am unable to accurately estimate my gas usage since this is a new, heavier hull than I had before. Also, most of my running in the TVA lakes last summer was limited since I was just trying to find my way around. This summer, I intend to run further and more often.
Thanks for all of the input and help. richg99