You can launch a small boat below the weir at Sardis and fish to the ramp at hwy 51. That should be an 8 or 9 mile trip. We use to fish this area before the weir when I was a kid.
You can launch a small boat at the end of the riprap at Enid and drag it up the bank at hwy 35.
The next ramp is on the floodway at Paducah Wells rd north of Charleston off of hwy 35.
The next ramp is at the Tallahatchee river and hwy 32 between Webb and Charleston. One map shows it opens up like a lake and another shows it all the same small river.
There's a ramp on hwy 332 where the Coldwater and Old Little Tallahatchie rivers come together. Go up the Tallahatchie a bit where you'll find the Old Yonoca river. It ought to be a good spot if the Asian Carp aren't bad.
Don't lock your motor down. Be ready to back up if your trolling motor is on the front of the boat.