Trim tabs are small surfaces connected to the trailing edge of a larger control surface on a boat used to control the trim of the controls, i.e. to counteract hydro- or aero-dynamic forces and stabilise the boat in a particular desired attitude without the need for the operator to constantly apply a control force. This is done by adjusting the angle of the tab relative to the larger surface. Boats with planing-type hulls will often have trim tabs attached to the trailing edge of the hull or transom. These are used to adjust the pitch attitude of the boat while underway. Changes in boat speed or weight placement will usually require the trim tabs to be adjusted to keep the boat at a comfortable and efficient pitch attitude. This reduces the work of the captain by reducing the amount of manual control necessary, as well as providing for greater efficiency by keeping the boat in the ideal orientation for the conditions.
Maintaining plane at a lower RPM is where the boat starts to achieve its maximum efficiency. Trim tabs provide the additional lift so that the throttle can be decreased without losing plane, adding both fuel economy and range. Some boaters have experienced as much as 30% fuel efficiency gains.
While in the past, trim tabs were most often found on cabin cruisers and sport-fishers over 25 feet, today they have become common equipment on boats 17-25 feet. You see trim tabs on everything from bass boats to bow riders, ski boats to center consoles. Many still believe that trim tabs are less important on smaller boats, but in fact the opposite is true. Trim tabs improve the ride of even the largest planing hulls, but on a smaller boat you will notice the difference much more. For instance, bigger boats are much less affected by weight distribution than smaller boats. After decades of use on the water, it’s been proven that all boats, large and small, benefit from trim tabs for the same reasons – they improve planing and fuel efficiency, they correct for uneven weight distribution, and they improve speed, safety and overall boat performance.