It's time to re-power.

[Blue_Runner]

In the gallery, in the 1994 Wellcraft manual for the V21, it shows that with the 60 gallon tank and a Yamaha 150 o/b (carbed) the cruise range is 199 miles at 8.0 gph. Is that Johnson a pre-1986 model??

That is well over the 100 - 140 miles you are looking for. Unless that Johnson is pretty old, it should give you that kind of range. But, on second thought, I think I know what you are saying cause you'd like to at least have a little left over after 100 to 140 miles rather than using every last drop!