Originally Posted by MBWhite
I'd take a wild stab and guess a month. Do you have crew and plan on motoring around the clock? Be a bit less time then but first time you run into a floating tree top or something (and there is always something) you might change the plan a bit.
You might find this site to be helpful:
Cruising the Mississippi River
It deals with the great loop tour but is informative about the Mississippi.
I believe it is around 1000miles from the Ohio
down but even a slow boat can manage 10mph (over ground) with the following current
, so 100mile days are possible without running at night (not recommended). In a rush and no mechanical issues and a couple weeks should be doable.
The big issue is finding places to tie up/anchor for the night and if you don't have the range, getting fuel
Most people take the Tenn-Tom as it's an easier and more scenic trip.