Trim tabs or boat stabilizers are rectangular stainless steel planes mounted on either side of the transom. On smaller boats, trim tabs may be fixed or manually adjustable, whereas for most boats measuring 22 feet or more, each trim tab is controlled via a cylinder linked to a hydraulic pump inside the engine compartment. The main purpose of trim tabs is to compensate for uneven weight distribution and correct the boat’s position at different speeds.
How they work
Getting on plane: When the boat has too much weight at the rear (caused by the engine weight, passengers and heavy cargo) and you want to get on plane without losing your front visibility, deflect the trim tabs downward to lift the boat out of the water. Once you reach cruising speed, pull the trim tabs back up, otherwise the boat will end up squatting and it will be hard to manoeuvre.
Correcting list: Boats with a deep-V hull and boats that are relatively narrow compared to their width may tend to list to one side at some speeds. Listing is aggravated when all passengers sit to one side of the boat. To correct the lean, activate the trim tab on the same side as the listing – this will help align the boat’s position as it compensates for the uneven weight distribution.
Reducing your cruising speed: Trim tabs can also help slow a boat while maintaining its comfortable plane position. For example, an engine that requires a minimum of 2,900 rpm to stay on plane and that is cruising at 26 knots will be able to maintain its plane at 2,650 rpm and drop down to 20 knots when the trim tabs are deflected downward.
Waves and storms: Trim tabs can also come in handy during storms or when navigating rough water. By bringing down the front end of the boat, you can reduce pounding and stress on the hull, as the boat will be in a better position when it enters the waves.
Improved steering control: Boats with two engines can be hard to manoeuvre and steer if one of the engines fails. Trim tabs can help correct an oblique trajectory when this kind of boat is forced to rely on a single engine.
High performance boats: Trim tabs are especially useful on high performance boats, which are typically long and narrow and feature heavy engine blocks (often with two or three engines) located at the rear of the boat. In these cases, trim tabs are essential for optimum boat performance. On high performance boats, each trim tab usually comes with its own powerful hydraulic (or electric) pump.
Additional information
Not all pleasure boats really need trim tabs. In fact, boats measuring 16-22 feet can usually get by without them, unless you’re using the boat for a very specific purpose. Trim tabs are more important on boats measuring 22-24 feet or more. As a result, most manufacturers offer them standard on longer boats. We recommend having them installed by the manufacturer or at a dealership, as it is important that you get the right type of trim tabs and that they be properly installed.
Purchasing trim tabs and having them installed costs at least $900-$1,200. Several manufacturers, including Bennett, Insta-Trim and Lenco, make replacement pieces and repair kits. These companies also sell trim indicators that will tell you the trims’ position.