Trim Tabs And Their Use

Trim Tabs And Their Use

Trim 1

Trim Tabs Play A Huge Role In Performance And Fuel Economy

Any boat worth its salt (or fresh water for that matter) has a set of Trim Tabs firmly attached to its transom. Without them (or their proper use), you’re relegated to a long day of plowing the water, all while multiplying your fuel costs.

Not only do they allow for a more efficient ride, but a much smoother and cost effective ride ride as well.

There are a number of trim tab systems available on the market but by far the most popular and well known are those produced by Bennett. Since 1960, Bennett Marine has been the world leader in trim tab technology and over the years has become a name that is synonymous with quality products. The trim tab systems that they manufacture are built to last and offer years of maintenance-free service.

Bennett trim tabs help your boat to operate at its fullest potential over a broader range of conditions. Having Bennett trim tabs reposition the boat’s bow to cut through the water, this offers you several advantages, including less drag and engine laboring, which helps increase performance and speed.

They offer greater comfort by reducing pounding and greater visibility. Trim tabs can also benefit you by helping to reduce fuel consumption. By maintaining plane at a lower RPM your boat is able to achieve maximum efficiency.

Trim tabs provide the additional lift needed so that the throttle can be decreased without losing plane, adding both fuel economy and range.
With trim tabs, some boaters have experienced as much as 30% fuel efficiency gains. Trim tabs give you more control and improve the performance of your boat by:
    • Getting you up on plane quickly
    • Allow you to plane at speeds lower than designed planing speed
    • Adjust the boat’s attitude for changes in speed, sea conditions and shifting weight
    • Correct listing on either side of the boat

Hydraulic Trim Tabs

Trim 2

Trim 3
There are two main types of trim tabs, electric and hydraulic. While Bennett Marine originally manufactured an electromechanical system, they eventually changed to hydraulic due to its many advantages and for the best interest of today’s boater.

Trim 4


Durability is the biggest advantage that hydraulic trim tab systems have over electrical systems. Electrical systems are more susceptible to damage when submerged. If the O-rings inside an electric actuator fail, water will flood the actuator.
Hydraulic actuators do not rely on a seal where the shaft enters the cylinder body, instead the seal is made on the piston face (inside the cylinder) where no marine growth can occur. If a seal on a hydraulic actuator should break, the cost to replace it is about $1.00 compared to the cost of having the entire electric actuator repaired.

Accuracy and Control

Bennett hydraulic systems are able to make precise adjustments needed for smooth safe control of the trim tabs. Hydraulic systems start and stop instantaneously so there is no lag time.

Speed of Operation

Hydraulic systems are ideal for applications where precise and reliable control is important, this is why racing power boats use hydraulic trim tab systems. Hydraulic systems are highly responsive and provide the boater with more control over the trim tab movement. At particularly high speeds, small, incremental adjustments of trim tabs are the key to getting the best results.


In the event of a failure, they hydraulic system can be safely retracted so the boat can run safely in a following sea or at high speeds. Also, because the Hydraulic Power Unit is located inside the boat, repairs may be made without the expense and downtime involved in hauling the boat out of the water.

Trim 5

Trim Tab Tips

  • Check the fluid level in HPU. With the trim tabs completely retracted the fluid level should be about 2 inches from bottom of reservoir (approx. 22 oz.).
  • Check for clean electrical connections on the back of the control, HPU ground wire, and quick-disconnect plug.
  • Cold temperatures do not affect the trim tab system, winterization is not necessary.
  • In saltwater, to deter electrolysis, a zinc anode should be attached to the top of each trim tab.
Paint trim tabs to discourage marine growth:
  • Clean surface of all grease, oil, dirt.
  • Apply two coats of epoxy metal primer.
  • Apply two coats of anti-fouling paint. Actuator, including the piston, may be painted.
  • Unpainted trim tabs may take on an orange discoloration, which is normal and should not be confused with the pitting and corrosion of electrolysis.


What size fuse does my trim tab system use?
On a 12 volt system use a 20 amp (24 volt will use 10 amp) in-line fuse on the power lead to the helm control.
If I keep my boat in saltwater, do I need to protect the trim tabs from corrosion? How?
Yes, you can protect your trim tabs from corrosion in saltwater by attaching a zinc annode to each tab. The zinc must make direct contact with the stainless steel, be sure not to ground trim tabs to other underwater appendages.
How do I tell the position of my trim tabs?
On smaller boats, it is usually easy to tell where the trim tabs are by visually sighting the horizon. Basically, you “feel” the boat’s attitude.
However, on larger boats, particularly those with raised helm locations, it is a bit more difficult to determine where the trim tabs are.
Trim 6

For more precise control Bennett offers three indication options:
  • Tab Position Indicator (TPI)
  • NMEA 2000 Indicator
  • Electronic Indicator Control (EIC5000)