Lake Lemon is one of my favorite local lakes, although I don't have my own boat yet, but have been on the banks, and out with buddies.
I have always caught something at Lemon, bass, cats, crappie, and sunfish. I can't say that about Monroe and Patoka.
The average is a about 8' deep, and there is a creek or channel that runs through the middle, which is deeper.
I always look for grass in Lemon, and usally toss Texas Rigged Zoom Trick Worms or Sweet Beavers, and my favorite emerald Chatterfrog. The average catch for me and buddies is 2.5-3 pounders, along the South and East side of the lake. I know there are bigger ones in there as well.
I won't say where exactly, but be sure to toss jigs around docks and boats, and worms through the grasses...there are plenty of targets around there.
Good luck and good fishing!