When I was there, I kept my boat at 3 places....
1. On base. The Outdoor Rec offers on base storage (not covered) for about $20 a month
2. In my garage (primary)
3. Lake Tuscaloosa....several places
I had a 2008 Moomba Outback V, and another buddy who had a Malibu....and neither one of us would dare park or drive our boat on/near Lake Columbus. Lake Lowndes was a great option to drop in for a quick run or two. Tuscaloosa is worth it's weight in gold -- tow the boat(s) there, on the water all day, stayed at the Yellowhammer Inn (they have a marina), etc...