Trim tabs, two planes installed on the transom of a boat to keep it level, help improve performance, fuel consumption, and ride. A level boat requires less fuel as it moves through the water, plus less stress will be placed on the hull and engine so your boat will perform at its best. The leveling effect eliminates that uncomfortable feeling you get when your load is not evenly balanced throughout the boat. An actuating cylinder deflects the trim tabs, raising the stern. As the stern rises, the bow lowers.
Most trim tabs use hydraulics for smooth trimming action.
When the control is released, the valves close, capturing the fluid in the actuators. Other systems operate in a similar manner using water pressure instead of hydraulic fluid. When properly installed, you will not be aware of this reverse function. The control function is based on the direction you wish to move the bow.