Twin Inboard Drives are two independent, side-by-side engines within a single boat and are very effective in close quarters. This effective twin drive setup uses two inboard engines, two propellers and two rudders.
With twin drives, you'll have two throttles and two gear shifts. Each throttle works its respective engine independently from the other and gives you a wide range of options. You'll quicky realize that in close quarters, your steering will be accomplished exclusively using engines, not rudders. For instance, you can rev your starboard engine to a higher speed and reduce your port engine to a lower speed. Or, you can shift your starboard engine to reverse gear and your port engine to forward. By applying power from each engine in differing amounts and directions, you can steer the boat in close quarters without turning the wheel and without any headway or sternway, advantages unique to this type of engine setup.
The pivot point on boats with twin drives tends to remain fixed when the gears are in opposite directions. When both engines are in the same gear, the pivot point tends to move as with a single-engine boat. For close-quarters maneuvering, using opposite gears with a fixed pivot point is easier than dealing with the pivot point moving forward or aft with every change of gear. Twin Inboards tend to be more effective for steering than outboards.
Prop walk is less of an issue with twin drives. Most twin drives are equipped with both a right-handed prop and a left-handed prop. This means that the prop walk created by one propeller is negated by the opposing prop walk of the other propeller as long as both drives are in the same gear.