How To Use Trim Tabs Correctly

Published at: April-11-2019

How To Use Trim Tabs Correctly

Properly sized trim tabs can significantly reduce the time needed to get up on plane.  They also allow the boat to keep its bow down and stay on plane at lower speeds (between 10-14 knots).  As the throttle increases, the stern of the boat begins to squat, lifting the bow.  By adjusting your trim tabs down the boat will react by lifting the stern, the bow comes down which improves your visibility, your speed increases and the engine will labor less which will increase your fuel efficiency.

The key to getting the best results from your trim tabs is to operate them in short half-second “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.  By operating your tabs in this manner you will avoid over-trimming, which occurs when you’ve deflected the tabs too far.  Be careful not to over-trim your boat.  An over-trimmed boat will “plow” or “bow-steer”.  If you over-trim the boat, simply press “Bow Up” and the bow of the boat will rise. 

A list can occur due to the following sea conditions, uneven weight distribution, water conditions,  passenger movements, prop torque, strong winds etc.  Since Bennett trim tabs may be operated individually you can easily bring the boat level by using your trim tab control.  If the port bow is high, then push the port side button on your control “Bow Down” direction.  If the starboard bow is high, then push the starboard side “Bow Down” direction until the boat is level. Bennett trim tabs operate the reverse of what you might think.  The port trim tab controls the starboard bow.  Conversely, the starboard trim tab controls the port bow.  The helm control should be wired so that all you have to do is press the control in the direction you want the bow to move “intuitively”.  You don’t need to worry about which trim tab is actually moving, just concentrate on the position of your bow.

"I don’t need Trim Boats for My Boat, I have Power Trim on my Outboard Engine."

This is a common misconception that if a boat has power trim on the outboard or outdrive it does not need trim tabs.  Yes, power trim can be used to adjust the boat’s attitude, but it is highly inefficient.  This is because a propeller is designed to force the boat forward.  When trimming the boat with the propeller, the propeller must not only push the boat forward but raise the stern, as well.  In this situation, prop slippage is greatly increased thereby wasting RPMs.  Also, power trim cannot correct listing and is ineffective at slower speeds.

For increased speed and power, use your trim tabs with your power trim.  The trim tabs trim the hull, while the power trim adjusts the propeller.  The result is optimum performance and efficiency not attainable by the use of power trim alone.  To achieve maximum performance

  • Adjust the trim tabs to achieve a planning attitude
  • Use the power trim to position the propeller path parallel to the water flow
  • If necessary, re-adjust the trim tabs to “fine tune” your bow’s position.

In other words, use your trim tabs to trim the boat and your power trim to trim your propeller.

Variations in Sea Conditions that effect a Boat’s attitude

These are tricky sea conditions that a boater needs to be aware of and then how to handle your trim tabs in these conditions.

Choppy Head Sea – for the most comfortable ride, when running into a head sea you will want to trim the bow slightly down, so the sharp forward sections of the boat do their work cutting through the waves.  This will bring the “V” of the hull in contact with the waves rather than having the waves pound the hull and your passengers.

Following Sea – For best maneuverability and maximum steering control, trim tabs should be fully retracted in a following sea, or when running into an inlet.  Keep the tabs up so the tide or current won’t push the stern from side to side. 

Beam Sea – Boats operating with waves approaching from the side often throw spray up on the windward side.    This spray often is carried aboard by the wind (particularly on smaller boats).  Trim tabs are used to raise the windward side of the boat, blocking the spray that blows over the boat, often resulting in a drier ride for you and your passengers.

Correcting for Porpoising – Porpoising is a condition more common in faster, performance boats.  As speed increases, the bow repeatedly rises out of the water until gravity overcomes lift and the bow bounces back down.  Press “Bow Down” in half second bursts, as the tabs are deflected, the porpoising subsides and your speed should remain the same or increase slightly.  Only a slight amount of trim tab deflection should be necessary.

Backing Down – When operating the boat in reverse, both trim tabs should be fully raised.  The trim tabs produce drag if they are left down in reverse.  This puts a strain on the tabs as well as affects the boat’s handling in reverse.  Additionally, if one tab is deflected more than the other in reverse, the boat tends to pivot around the deflected tab.  Properly installed tabs, when fully retracted should not have any effect on backing down.

Remember, when using properly sized trim tabs you will get up on plane quickly and correct for listing at nearly any speed, regardless of weight distribution or sea conditions.  These benefits add up to reduction in drag, reduced engine stress, increased speed and decreased fuel consumption. 

So get out on your boat and enjoy the ride!