Trim is the angle, or lean, that a boat has when sitting in the water. Trim can be either side to side or fore and aft.

Side to side trim is known as the “list angle.” A boat that leans to one side is said to be listing to port or starboard. Listing can be controlled by properly distributing any moveable weight in the boat, such as passengers, fuel cans, heavy equipment, or freight. A boat that is listing is more likely to capsize when hit with waves, wind, or even the wakes from another boat.

Fore and aft trim is controlled mechanically. Most powerboats have a trim switch, which is often included as part of the throttle lever. Operation of the trim switch will move the outdrive unit or the trim tabs up or down, to adjust how high the bow rides over the water.

Trimming down pushes the bow down into the water, and gives the propeller the best bite. The trim should be in the full down position when accelerating from a stop. Trim down when pulling a skier out of the hole, while making sharp turns, and when boating in rough water.

However, when cruising at planing speeds, trimming the bow too far down will increase drag and engine strain, and will reduce the boat’s top-end speed. Trimming up lifts the bow out of the water, and allows the engine to run more efficiently. With less of the hull in contact with the water, the boat has less drag and can reach higher top speeds. Trim the bow up when the boat is cruising at planing speeds in smooth water, and when running at full throttle.

Trimming too far up may cause the bow to bounce up and down, also known as porpoising. The boat will not be nearly as controllable or stable in turns.

Accelerating from a stop with the trim up will force the bow high up out of the water. Not only will the skipper’s vision over the bow be completely obstructed, it will be almost impossible for the boat to reach planing speed. A recreational boat will almost certainly not be able to pull a skier out of the water when the trim is up.

A trim gauge on the boat’s console allows the skipper to visually identify the trim position of the outdrive or the tabs. If your boat does not already have one, installing a trim gauge would be a useful addition.

Skillful skippers are constantly adjusting the trim to accommodate changing water conditions and different boating maneuvers. Experiment with your boat’s trim while under way. The correct trim should be discernible to you in the sound of the engine and in ride quality.

Even small trim adjustments can make a world of difference on engine wear, gas mileage, safety, and passenger comfort. Most of all, proper trim control will permit the boat to deliver its best possible performance.