An outboard motor with power tilt and trim has two pistons on the engine bracket that change the angle, or "trim" of the motor. A third piston "tilts" the engine--raising it out of the water by tilting the top of the engine down and the bottom up toward the surface. Trim changes the angle at which a boat is pushed through the water--bow (the front) up, or bow down. Well-adjusted trim creates a smoother ride and proper tilt allows you to enter shallows without damaging the prop.
Trim the engine down as far as you can by pressing the bottom of the trim button located on the throttle handle. Accelerate slowly to a normal cruising speed. Tap the upper half of the trim button to trim the motor upward in small increments.
Monitor your speed on your GPS. The speed will increase as your boat's hull finds its most efficient angle in relation to the water.
Tap the lower half of the trim button on the throttle to trim your engine downward if the boat's speed decreases. Tap until the speed increases once again.
Press the top of the tilt button, located on the base of the throttle to tilt your engine up. Tilt your engine upward out of the water to operate your boat in shallow water, or to raise your motor when you bring the boat onto its trailer. To tilt your engine downward into the water, press the bottom of the tilt button.
In heavy seas, boats generally ride best with neutral trim and tilt--the whole boat rides over the waves (called "being in step with the sea") without the stern (the back end) taking on water, or the bow flying high over the waves (called "porpoising" because it resembles a porpoise leaping from the water).
If you feel the nose of your boat trying to "bury" itself in the water, increase your trim. If you feel the back of your boat trying to bury its stern (called "squatting"), decrease the trim.