You can adjust speed and the amount of line you have out to control depth. With about 60-70 feet of line out at 1.2 mph, my baits run 4-5 feet deep depending in if they are tubes or curly tails.
If you want to keep the jig near the bottom, I would switch to titelining and use 1/2 to 3/4 ounce in line weight to keep the jig down and still be able to troll at about 1 mph.