Trimming a boat
Trim is the running angel of the boat as it makes way in the water. Trimming a boat means to either raise or lower the bow, hence adjusting the angle of the boat with water level. The most efficient pitch attitude, changes with speed so trim tabs are adjusted based on speed and weight displacement to maintain an efficient pitch attitude.
A pair of movable ‘flaps’ mounted on the transom of a boat. When interacting with the water they deflect the flow of water along the boat. When lowered, the tabs create lift at the stern, lowering the bow. Along they create drag, reducing the efficiency of the hull shape.
The capability of outboards and sterndrives to adjust the angle of thrust by tilting it ‘out’ or ‘in’.