2 to 3 miles per gallon depending on what you do on any given outing.
Pulling a tube around is of course worse since you tend to start and stop a
lot. Might get closer to 3.5 on a long run at around 3500 rpms.

Get an inexensive handheld GPS. This will let you know exactly how far you
have traveled on any given outing and then when you fill up you will know
exactly what your fuel consumption is. Plus it gives you a true speed
reading. Plus you know exactly how far you can go on a tank of fuel. Plus
you know where you are on any new lake you might go to.

--
Tony
my boats and cars at http://t.thomas.home.mchsi.com

-
"Captain Chaos" wrote in message
...
I'm looking to buy a late 80's 19' runabout with a Chevy 350 motor.
Intend to tow an inflatable, cruise the lake, and occasional fishing.

How much fuel can I expect to consume cruising at 20-25 mph? How less
fuel efficient would this boat be compared to one with a smaller
motor?