How To Use Trim Tabs


Stern-mounted trim tabs can be a captain's best friend. These hydraulically operated metal plates work by offering resistance to the water on either or both sides of the stern as the boat moves, thus raising the affected part of the stern and bringing the bow down. They are used to find a powerboat's optimum attitude, can help to adjust for any listing of the boat due to uneven weight distribution, prevent "porpoising" (an up-and-down cycling movement of the bow) and offer the skipper options to deal with sea conditions.

Things You'll Need

  • Hydraulic trim tabs installed on your boat
  • Assess the degree to which your boat is planing when you have reached your desired speed. If he stern is riding too low in the water and the bow is sticking way up, use half-second bursts simultaneously to both the starboard and port trim-tab controls labeled "Bow Down" or "Down," waiting a short while after each burst to see how the boat responds. Continue until the boat reaches the desired attitude.

  • Avoid over-trimming. If the boat seems to be excessively plowing though the water, and exhibits "bow steer," use half-second bursts on both the starboard and port "Bow Up" or "Up" trim-tab controls together until the problem is resolved.

  • Use the trim tabs individually to correct listing problems (situations where the boat is leaning to one side or the other). If the boat is listing to port, or the starboard bow is high, use the port trim-tab control labeled "Bow Down" or "Down" to bring the starboard bow down. For a problem where the port bow is high, use the starboard trim-tab control labeled "Bow Down" or "Down" to correct the list.

  • Respond to sea conditions by using the trim tabs. In head seas, trim the bow down so that the boat's prow meets the waves and slices through them. In following seas, fully retract the trim tabs. In beam seas (waves from the side) use the trim tabs to raise the windward side of the boat (by using either port or starboard "Bow Up" controls) so as to block the spray that may be blowing into the boat.

  • Correct porpoising with short half-second bursts on the "Bow Down" or "Down" controls for both port and starboard simultaneously. Usually only a slight amount of trim-tab deployment is necessary to correct this problem.

Tips & Warnings

  • Always fully retract the trim tabs when operating the boat in reverse. The drag caused by the trim tabs being down puts a strain on the trim tabs, and if one trim tab is down more than the other, the boat will pivot around the trim tabs, causing a potentially dangerous situation.

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