A trim tab presses down on the water coming off the transom, lifting that side of the boat — effectively changing the running surface to suit changing conditions. Independently controlled trim tabs compensate for differing loads and hold the boat’s attitude in crosswinds or crossing seas, easing the captain’s job of giving his crew a smoother ride. Using trim tabs is much like riding a bicycle. You learn to do it by feel. Your knot meter will tell you when you have trimmed for best speed at any throttle setting and your common sense will help you adjust trim to sea conditions and weight distribution.
The key to obtaining optimal results from trim tabs is to operate them in short bursts and let the boat react before making another adjustment. The amount of time between corrections is influenced by the size of the trim tabs and the boat’s speed. This will help avoid over-trimming or ending up with one tab too far down when correcting lateral trim. You will quickly become acquainted with your boat’s particular traits.
Getting Out of the Hole
When you advance the throttle, the stern of your boat begins to squat, lifting the bow. As the boat accelerates, push the “bow down” position of the trim tab control in short bursts. The boat reacts by the stern lifting, the bow coming down, speed increasing, and reduced engine laboring. If you over-do it and deflect the tabs too far the boat will end up over-trimmed. The steering will become over-sensitive and the boat will want to pull off course to port or starboard. If this occurs, operate the control “bow up” until the desired attitude is established.
Adjust the trim tabs to achieve the desired running attitude. When your boat is running untrimmed the bow spray will exit the sides of the boat far aft. You’ll throw a big wake that curls like a breaker on the beach. The rooster tail is high and close to the stern. The engine labors and the ride tends to be less smooth. Once you’ve trimmed the boat, the bow spray moves forward and is flung not as far from the boat. The wake diminishes in height and the rooster tail flattens out and moves away from the boat. The engine is operating under less load as evidenced by the tachometer and speed.
When running into the waves you’ll want to trim the bow down so the sharp point of the bow can cleave the waves. This provides the most comfortable ride and minimizes stress on the boat (and passengers). In a following sea the tabs should be fully retracted for maximum steering response. This also helps to prevent your boat from burying its bow while overtaking waves.
Your trim tabs can also be used to correct any list of the boat due to weight distribution of crew, tanks or gear. If the boat lists to starboard, for example, adding starboard tab at speed (or lowering the starboard trim tab) will cause the boat to level off. As before, make the corrections in bursts and allow the boat to settle to the new settings.