Published at: February 12, 2019

How do you determine the correct trim tab size?

Installing undersized trim tabs is one of the more common mistakes.

A tab that is too small will have to be deflected more in order to create sufficient lift. When making a choice between trim tab sizes, the largest trim tabs that will comfortably fit on the transom will be the most efficient.

Just remember, the larger the trim tab the more lift it will produce with the least amount of drag.

Determine space on your transom

In order to determine correct size for your trim tabs, you should determine the space available on your transom.

Height Clearance

Before purchasing trim tabs, make sure there is room on the transom to place the tabs and verify there is enough height allowance to mount the actuators.

Checking for mounting obstacles on your transom

Measure the amount of span (side to side) measurement you have available on the transom. Check the clearance in regards to transducers or platform brackets which might hinder the mounting of the tabs. Next, check to see if the chord (fore to aft) measurement will have any restrictions like ladders or swimming platforms once lowered.a

Where to mount the trim tabs

Trim tabs should follow the Vee at the junction of the transom and the bottom of the boat. For maximum side to side control, trim tabs are generally mounted 3-4” from the chine and run towards the keel.

It is OK to mount the trim tabs across the strakes.

On boats powered by outboards it is necessary that the trim tabs not be placed too close (minimum 8”) to the lower unit to avoid disturbing the water flow to the propeller.

You now have determined how much space on your transom is available for a trim tab.

If you are uncertain of your measurements please consult with a trained maintenance technician or contact Exalto Emirates.

Determine Size of the trim tab

Now that you have determined how much space is available, you now need to determine the size of the trim tab.

Many factors affect the choice of properly sized trim tabs, and the ultimate responsibility for the selection is up to you.

Check the sizing recommendations from Bennett Marine and remember these sizes are based on an average performing boat.