How to Install Trim Tabs

Posted: June 1, 2012

They’ll make your boat perform better, and you can mount them yourself.

By: Capt. Wilson Sheppard

There are two types of trim tab systems: hydraulic and electromechanical. As with most things boat-related, which system is better is widely debated, and personal. When I bought my boat, the hydraulic trim tabs were not working, which was no good, because I expect trim tabs to allow me to get on plane faster and be able to compensate for uneven weight distribution.

I chose an electromechanical trim-tab kit from Lectrotab (lectrotab.com), which features many component options for new installations or updating existing systems. My kit included two 12-inch-by-18-inch stainless steel trim tabs, two actuators with 28 feet of wire and an oval control unit with auto-retraction programming, LED indicators and an auto-dimmer photocell.

Here’s how you can overhaul the ride and performance of your boat in an afternoon. That is, if all goes well. Remember, this is boating, and Murphy does have a law.

Step 1. Getting Started

If you don’t currently have trim tabs, you can begin with Step 2, where the actual installation begins. If you have trim tabs, you have to put in a little extra elbow grease to remove the previous setup and prepare the transom for the new equipment. If your existing system has any damaged screws, you can search boating websites and forums or ask a boat professional for removal ideas. After removing the equipment, carefully use a paint scraper or razor to remove excess adhesive sealant from the transom. Then, fill any unneeded holes with resin.

Step 2. Installing the Trim Tabs

Make sure there are no obstructions inside or outside the transom that would interfere with the trim-tab system. The tabs should be mounted outside the steering angles of your outdrives or outboards. If your boat is docked in a wet slip, you may consider applying antifouling paint and adding zincs to the trim tabs.

The tabs should be mounted a few inches from the outward edge of the transom and about 1/4 inch above the bottom edge. Drill pilot holes for the two outward holes on top of each hinge plate so you can temporarily mount the tabs and mark the remaining holes. When you are ready to permanently mount the trim tab, remove the tabs before drilling the pilot holes. Put 3M 5200 adhesive sealant on the hinge plate and the screws. Drive each screw straight and do not overtighten.

Step 3. Mounting the Actuators

Mount an actuator on a trim tab, and connect the transom bracket to it. Use a pencil to mark the position of the bracket and the screws on the transom. Remove the actuator from the bracket and trim tab, and then drill pilot holes. Apply 5200 to the bracket and screws, then connect the bracket, actuator and trim tab. Repeat this process for the other trim tab. You can apply antifouling paint to the actuators, but make sure they are fully retracted, and do not paint any exposed ram.

Step 4. Wiring the Control Unit

If you previously had trim tabs installed, you should be able to use the existing holes to run the wiring. If not, you will have to drill holes through the transom, so be sure to check for anything that could be damaged by the drill bit.

You will notice that each actuator’s wire bundle has a black wire, a white wire and a tube. The tube is connected to a check valve that allows air to enter the actuator but does not allow air to exit. Make sure the tube is not pinched as you are installing it. Use 5200 and a clamshell splashguard to seal the hole and prevent water intrusion.

To wire the control unit, use 1/4-inch push-on female connectors for the seven terminals on the back of the oval control unit. There are terminals for positive and ground connections to your DC power source. Use 14 AWG wire or higher for these two connections. In a 12v system, these connections should be run from a 20-amp fuse or breaker on the distribution panel. There is a terminal called an auxiliary connection, but it actually powers the auto-retraction and indicator synchronization functions of the control unit. Do not use a jumper from the positive connection above or wire it to the ignition switch. It should be wired to the switch used to turn the entire trim-tab system on and off. The remaining four terminals connect to the black and white wires from the actuators. You can use a four-wire connector from Lectrotab or connect the actuators directly to the control unit. Use 12 AWG or higher wire to lengthen the actuator wires. Complete the installation by securing the wired oval control unit to its position at the helm.

Step 5. Testing the Installation

To test the operation of the system, turn on your DC power and the switch controlling the trim-tab system. The control unit should initiate a 10-second calibration sequence to fully retract the trim tabs and synchronize the LED indicators. Once the system is online, check the operation of both trim tabs throughout their entire range of motion. Pressing the Bow Down button of the port or starboard switch should move the corresponding trim tab down. Pressing the Bow Up button of either switch will raise the appropriate tab. Last, when the trim-tab control switch is shut off, another 10-second calibration sequence should fully retract the tabs.

Immediately after spending an afternoon installing the trim tabs, I took a brief sunset cruise. I was pleased to be able to get on plane faster at lower rpm. Trim tabs definitely make a difference in the performance of my boat.

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