How is boat performance affected by outdrive trim angle?

Time to plane, top speed, and handling are all performance aspects relating to the trim angle of the drive(s). The drive should be trimmed in, for the best “hole-shot” acceleration and shortest time to plane. This practice forces the bow down and the stern upward and places the propellers at the most efficient angle for pushing the boat's hull on top of the water (on plane). Once on plane, the drive should be trimmed out, thereby placing the props in the best position to provide optimum performance. If the drive(s) is trimmed in too far, the boat will run too wet or too deep in the water. In this condition, top speed and fuel economy decrease, and the boat may bow steer in one direction or the other. As a result, steering torque is likely to increase. Conversely, if the drive(s) is trimmed out too far, the stern of the boat will be lowered and the boat's bow may begin to 'bounce' up and down - a condition known as 'porpoising'. Either extreme once on plane will result in less than ideal performance characteristics. In general, top speed and handling will be realized when the prop shaft (stern drive boats only) is positioned parallel with the surface of the water.

updated: 4/1/2008