What is a trim tab on a boat

A BETTER RIDE

WITH BENNETT TRIM TABS

Properly sized trim tabs improve the performance of your boat by adjusting the running angle of your vessel. Bennett Marine trim tabs help you get on plane faster, correct listing (roll), improve visibility, and increase overall efficiency and control.

• Get on plane quickly to see over the bow
• Increase vessel performance and efficiency
• Correct listing (roll)
• Adjust the boat’s attitude for changes in speed, sea conditions, and shifting weight
• Correct porpoising (rhythmic bouncing)

Properly sized trim tabs improve the performance of your boat by adjusting the running angle of your vessel. Bennett Marine trim tabs help you get on plane faster, correct listing (roll), improve visibility, and increase overall efficiency and control.

• Get on plane quickly to see over the bow
• Increase vessel performance and efficiency
• Correct listing (roll)
• Adjust the boat’s attitude for changes in speed, sea conditions, and shifting weight
• Correct porpoising (rhythmic bouncing)

SYSTEM COMPARISON

Whatever your need or preference, we’ve got a system for you, all available with a wide variety of tab sizes and control options

Exceptional electric systems designed to outperform the competition.

Designed for limited transom space. Less than 6.5″ vertical space required.

Our original and time-tested durable and dependable hydraulic systems

Sophisticated black powder-coated hydraulic Performance Tabs.

High-performance Premier Line XPT stainless steel hydraulic trim tabs

Custom Premier Line stainless steel BXT hydraulic systems

Premier line SST stainless tabs designed for mega-yachts

TAB SIZING GUIDELINES

General guidelines for choosing a trim tab size

In general the widest span tabs that will fit on the transom will be the most effective. The greater the surface area, the greater the lift. We‘ll typically recommend a 9” chord tab, but depending on available transom space a shorter or longer chord tab, or specially shaped tabs with upfins or dropfins may be advised.

As a general rule for boats with max speeds of 40MPH, choose at least one inch of trim tab span (per side) for every foot of boat length. For example, a 22′ boat would use a 24”x9”.
For speeds 40MPH and over, we’ll generally point you to one of our Performance, or Premier Line high-performance systems.

Measuring available transom space and considering limitations

Choose the approximate tab size for your boat using the sizing chart below. Make sure the tabs will fit your transom using the diagrams shown as a guideline. When measuring, disregard the strakes and follow the Vee of the hull.

The sizing guidelines below are intended to assist in the selection of tab sizes for vessels that do not currently have tabs installed by the boat manufacturer. For assistance with unique applications not outlined below, please call us.

When 12" chord tabs are recommended

The 9″ chord is used in most applications. However, in certain circumstances the 12″ chord may be more effective:

• Limited Transom Space – Boats with twin outboards or twin I/Os, or boats with transom configurations that limit trim tab span, can use 12″ chord tabs to achieve maximum lift. Using the measuring guideline above, fit the maximum span tab and use the 12″ chord.
• Extra Lift – Slower boats (less than 15 mph), semi-displacement hulls, boats over 50 feet, outboard brackets or boats with any other feature that increases the need for lift aft benefit from the 12″ chord. The 12″ chord provides greater surface area, thereby utilizing more water flow and providing more lift.

Trim Tab Mounting Options

Two types of mounting hinges are available:

• Transom Mount – This hinge style fits to the boat’s transom and is used in the majority of applications.
• Bottom Mount – Used only when transom mount is not practical; requires a flat bottom with no strakes or other protrusions.

USING YOUR TRIM TABS

Trim tabs are super-easy to use and after just a few times using will become second nature. The concept is simple but the results are impressive! Benefits include: planing faster at slower speeds, reducing bow rise, correcting listing, correcting chine walking, correcting porpoising, and more. Enjoy the ride!

Making Small Adjustments

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.

Curious about automatic trim tabs? Try AutoTrim Pro, it’s like cruise control for your trim tabs.

Finding Optimum Attitude & Avoiding Over-trimming

Operating your tabs in small adjustments (see above) will help avoid over-trimming, which occurs when you’ve deflected the tabs too far. 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.

Your boat may have been built to avoid this situation. Bennett’s adjustable trim tabs enable a boat to be designed and rigged so it never runs in an over-trimmed condition even at the top end of its speed range. This avoids the hazardous combination of high speed and unpredictable handling.

Curious about automatic trim tabs? Try AutoTrim Pro, it’s like cruise control for your trim tabs.

Trimming From a Bridge or Tower

When steering from a bridge or tower, a good trimming method is to watch the bow spray, stern wake, or the rooster tail. An untrimmed boat will produce more spray aft of the bow and it will produce a larger wake. When trimmed, the bow spray is farther forward, the wake is reduced, and the rooster tail is smaller and farther behind the boat. You’ll also notice that the engine RPM will increase when the boat is properly trimmed.

Curious about automatic trim tabs? Try AutoTrim Pro, it’s like cruise control for your trim tabs.

Correcting a Listing Condition

As a result of uneven weight distribution, prop torque or wind, a boat can run with a list. Deep “V” hulls are particularly vulnerable to this condition. Running with a list is uncomfortable, as well as unsafe. Bennett Trim Tabs operate independently for effective list correction.

You can easily bring the boat level using your control. If the port bow is high, push the port side “Bow Down” direction (this lowers the trim tab on starboard side). If the starboard bow is high, push the starboard side “Bow Down” direction until the boat is level (this lowers the trim tab on the port side).

Curious about automatic trim tabs? Try AutoTrim Pro, it’s like cruise control for your trim tabs.

Correcting 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 down, creating a rhythmic bouncing effect. Press “Bow Down” in half second bursts. As the trim tabs deflect, the porpoising subsides and your speed should remain the same or increase. Only a slight amount of trim tab deflection should be necessary.

Curious about automatic trim tabs? Try AutoTrim Pro, it’s like cruise control for your trim tabs.

During Take-Off

Properly sized trim tabs can significantly reduce the time needed to get up on plane. They also allow a boat to keep its bow down and stay on plane at lower speeds.

As the throttle is advanced, the stern of the boat begins to squat, lifting the bow. As the boat accelerates, push the bow down position of the helm control in short bursts. The boat reacts by the stern lifting, the bow coming down, speed increasing and the engine laboring less.

Curious about automatic trim tabs? Try AutoTrim Pro, it’s like cruise control for your trim tabs.

Using Your Power Trim and Trim Tabs Together

It 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 prop, the prop must not only push the boat forward but raise the stern as well. In this situation, prop slippage is greatly increased thereby wasting RPMs. Power trim also cannot correct listing, and is ineffective at slower speeds.

For increased speed and power, use your trim tabs WITH your power trim. Bennett Trim Tabs, in combination with power trim, enable both the hull and prop to be trimmed independently. The trim tabs trim the hull, while the power trim adjusts the prop. The result is optimum performance and efficiency not attainable by the use of power trim alone.

To achieve maximum performance:
1. Adjust the trim tabs to achieve a planing attitude.
2. Use the power trim to position the prop path parallel to the water flow.
3. If necessary, re-adjust the trim tabs to “fine tune” your tabs. In other words, use your trim tabs to trim the boat and your power trim to trim your prop.

Curious about automatic trim tabs? Try AutoTrim Pro, it’s like cruise control for your trim tabs.

Using in a Choppy Sea

For the most comfortable ride, when running into a head sea you want to trim the bow down so the sharp forward sections of the boat do their work cleaving 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.

Using in a Following Sea

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

Using In a 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 vessels). Trim tabs are used to raise the windward side of the boat, blocking the spray that blows over the boat, resulting in a drier ride.

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 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, fully retracted have no effect on backing down.