How to Trim Your Boat for Optimal Performance

Learning how to properly trim your boat will give it more MPH and MPG

Whether your boat has a Mercury outboard or a MerCruiser sterndrive, the propeller’s angle of attack in the water can be changed by the driver — called trimming — to meet different conditions. Learning how to properly trim your boat is one of the first skills a new boater should learn.

Couple Riding in Bayliner Trophy Center Console Fishing Boat, Portside View, Boat Underway

Prepare for launch

When getting ready to get on plane, the driver should put their hand on top of the throttle lever and place the thumb on the rocker switch button, which is called the trim switch. This button allows the driver to change the angle of the outboard or lower unit of a sterndrive. For launch, press the bottom of the switch to “trim down,” also known as “trim in” until it’s at its stop. This will help push down the front of the boat (also called the bow) when power is applied and helps it to get on plane faster. For launch, drivers should quickly advance the throttle all the way and then back off to the desired speed after the boat is on plane.

Couple Riding in Bayliner Trophy Center Console Fishing Boat, Starboard View, Boat Underway

Trimming at cruise speeds

Once the boat is on plane, if the trim is still down, the bow will plow the water and steering will feel hard. This can be quickly remedied by pressing the upper part of the trim button. When the bow rises and the steering feels lighter, that means less of the hull is in the water, which greatly reduces drag and improves fuel economy. The driver will notice the RPM and speed will also increase. Keep trimming until the speed starts to fall, which will also be accompanied by a spike in the RPM and the sound of the prop cavitating will be heard. When that happens, trim down a little and the speed should rise again. By doing this, the driver will know where the upper end of the boat’s trim range is for that speed.

Couple Riding in Bayliner Trophy Center Console Fishing Boat, Starboard-Stern View, Boat Underway

Finding the sweet spot

While trimming a boat to its upper range will give the best speed and fuel economy, its steering may be less effective so its ability to dodge a floating obstruction or navigate a twisty river may be compromised. If the boat’s bow is rising and falling (called porpoising), this is an indication the trim is set too high. A boat running too bow-high in choppy or rough water conditions may pound rather than slice through the waves. All of these conditions can be remedied by trimming down a little.

 Couple Riding in Bayliner Trophy Center Console Fishing Boat, Port-Side Bow View, Boat Underway

Active trim

Both MerCruiser sterndrives and Mercury outboards (40hp and above) have an available option called Active Trim, that automatically trims the boat. When activated, during acceleration, the trim goes up and when decelerating or making a turn, the trim goes down. The driver can override Active Trim at any time by pressing the trim button on the throttle and different trim profiles can be selected for different conditions or driver preferences.

Knowing how to trim your boat will not only unlock its best performance but will also save money at the pump.