The speed and range of your boat makes a huge difference. A boat with a 300mile range that can cruise
at 15kts will get there a lot faster than a boat that has a 5kt cruise.
You don't want to run any of the rivers at night. Too much debris. You also are limited in some areas by spacing of safe anchorages/marinas. If you have 2hrs of light left but there is no safe place within 2hrs range, you have to stop early. The later you can push towards June, the better as you get more hours of light to work with.
Also, in April, spring flooding can create an issue. We got stuck in Grafton Il for 2 weeks until the corp of engineers would allow us thru. The later you wait the less flooding is a concern.
From Chicago, you take the Illinois River. There are several locks and the current
is fairly tame. Around 330miles.
From Grafton (where it meets the Mississippi), it's around 150 miles to the Ohio
River. No locks south of St. Louis and the current
can add 2-4kts, so even fairly slow boats can make 80-100miles in a day.
At the Ohio you have a choice:
- At the Ohio River, you can continue south but services for pleasure boats become very rare on the Mississippi. You get the advantage of lots of favorable current and no locks but the river curves back and forth drastically increasing the miles to get from A to B.
- If you head
up the Ohio, once on the Tennessee River, there are plentiful anchorages
. While it's not dead straight, there is less curving than on the Mississippi. I haven't checked the milage but it's probably not that much more.
I would seriously give thought to the tenn-tom route. If you push hard 3-4wks is possible but only if everything goes perfect. Engine
issues or a lock getting shut down could easily add weeks.