How to Mount a Transducer to a Trolling Motor

How to mount a transducer to a trolling motor comes down to five jobs: fit the trolling motor bracket to the transducer, strap the bracket to the motor’s lower unit with a clamp, point the transducer the right way and set it parallel to the bottom, run the cable up the shaft with slack at the pivot, and check everything on the water. This guide walks through each step using Garmin’s installation instructions, covers how live sonar transducers differ, and explains what to look for after the install. Your transducer’s own instructions come first; where they differ from anything here, follow them.

Safety note: this guide covers the mechanical mount only. It does not cover wiring a transducer, sonar module, or trolling motor to power. Follow the instructions that came with your products, and use a qualified marine installer for any electrical work you are not sure about.

Before You Start: Parts, Tools, and Power

First, confirm your transducer is meant to go on a trolling motor. Some transducers ship with a trolling motor bracket. Garmin’s STRIKER 4 product page, for example, lists transom and trolling motor mounts in the box with the dual-beam transducer. If your transducer only came with a transom bracket, check whether the maker sells a trolling motor mount for it before improvising one. Also check your motor: some trolling motors have a transducer built into the lower unit (Garmin’s Force manual, for example, describes a transducer secured with the nose cone at the bottom of the motor), so a clamp-on unit may be unnecessary.

The hardware varies by transducer, so read the parts list before you begin. Garmin’s two transom and trolling mount sheets show the range:

• The Garmin transom/trolling mount transducer installation instructions for its GT30 and GT34UHD transducers call for a hose clamp and cable ties, both marked as not included.
• The Garmin transom-mount transducer installation instructions for the dual-beam bracket use a long cable tie, smaller cable ties, and a gasket from the kit. They add that in cold water or in areas with heavy timber or debris, you should use a metal 4 to 5 in. worm gear clamp (not included) instead of the cable tie.
• For holding the cable to the shaft, the dual-beam sheet recommends black electrical tape above and below the rotating joint, because zip ties and cable clamps can over-tighten and damage the cable.

You will also need a screwdriver or nut driver that fits your clamp. Then deal with power. You will be working next to the propeller, and Garmin’s Force trolling motor owner’s manual says to always disconnect the motor from the battery before handling or working with the propeller, propeller drive motor, electrical connections, or electronics enclosures. Whatever brand your motor is, disconnecting it first is the cautious way to do this job; check your motor’s manual for its own warning. The same Force manual also warns never to run the motor with the propeller out of the water.

How to Mount a Transducer to a Trolling Motor, Step by Step

These steps for attaching a transducer to a trolling motor follow the trolling motor sections of the two Garmin sheets above, for a standard transducer that straps to the motor body. Do the work with the motor deployed or laid out where you can reach the lower unit comfortably.

1. Attach the bracket to the transducer. On the GT30-style mount, Garmin has you fasten the trolling motor mount to the transducer with small M4 screws and star washers, then route the cable through the cable exit so it sits on the top side of the motor housing when stowed.
2. Thread the clamp. Push the hose clamp or cable tie through the slot in the mount until equal lengths stick out on both sides.
3. Seat the gasket if your kit has one. The dual-beam sheet places a gasket on the curved top of the mount, between the mount and the motor body.
4. Point it the right way. Set the mount against the body of the trolling motor with the narrow end (Garmin’s dual-beam sheet says the front) of the transducer pointed away from the propeller. Check it twice before you tighten anything.
5. Tighten the clamp around the motor body. Wrap it around the lower unit and snug it. On the dual-beam kit, Garmin has you leave the long tie loose at first, line up the gasket, then tighten and trim the excess.
6. Set the angle. Position the transducer so it is parallel to the bottom when the motor is in use. On the dual-beam bracket, Garmin says to then tighten the locking nut until it touches the bracket and give it 1/4 turn more, and not to overtighten.
7. Optional: seal the front of the mount. The dual-beam sheet says that if necessary you can fill the forward-facing part of the mount (not the cable tie pocket) with sealant so debris does not collect there.

On a bass boat with a bow-mount motor, that can mean kneeling on the deck with the motor deployed over the side; on a jon boat with a transom-clamp motor, you may be able to tilt the motor up and reach the lower unit from inside the boat. Either way, have the clamp, ties, and tape within reach before you start, so one hand can hold the bracket in position while the other tightens.

Routing the Transducer Cable Up the Shaft

The cable needs the most care, because the motor turns, tilts, and stows. Garmin’s instructions are consistent on a few points:

• Secure it to the shaft. The dual-beam sheet uses the smaller cable ties to hold the transducer cable to the motor shaft.
• Leave a service loop at the pivot. The dual-beam sheet says to secure the cable above and below the pivot joint and create a service loop at least 10 in. long, with the rotating joint centered on the loop.
• Do not let it get pinched. Both sheets say the cable must not be pinched when the trolling motor is deployed or stowed.
• Keep it away from other wiring. Garmin says not to route the cable close to electrical wires or other sources of electrical interference, and the GT30 sheet lists trolling motor batteries and wires among the things to stay away from.
• Do not cut it. Garmin says cutting the transducer cable voids the warranty. Coil the extra length neatly near the display instead.

Before you call the job done, stow and deploy the motor a few times, then turn it through its full steering range by hand with the power still disconnected. Watch the cable at the pivot, the mount, and any point where it crosses a bracket. If it pulls tight or rubs anywhere, add slack or re-route it now.

Mounting a Live Sonar Transducer on a Trolling Motor

Live sonar transducers use different hardware. The Garmin LiveScope 2 installation instructions describe two main trolling motor options, plus a bottom mount for Garmin’s Force Kraken motor:

• Barrel mount. A rubber liner goes against the motor barrel, a hose clamp holds the barrel mount, and arrows inside the mount must point upward. The transducer attaches with a hand-tightened knob. Garmin says this position supports forward and downward views but not perspective view.
• Shaft mount. A two-piece bracket clamps around the motor shaft with its arrows pointing up and its notch lined up with the groove in the shaft. Garmin recommends the rubber liner for shafts smaller than 1.5 in. and says the perspective mount does not support shafts smaller than 1.25 in. It also says to mount the transducer as far from the motor as possible to avoid obstructions in the sonar image, then cycle the motor from deployed to stowed and back to check the bracket position.

The same instructions add a few rules that matter on any motor: the cable must not touch the propeller when the motor is running, you should leave slack so the transducer can rotate between views, and Garmin warns that damage or loss from third-party or self-fabricated mounts is not covered under warranty. It also notes that the compass may not work if the transducer is mounted on the motor. A LiveScope 2 transducer also needs its own power connection; follow the wiring section of your instructions, or hand that part to a qualified installer.

Checking the Install on the Water

You cannot confirm the mount in the driveway. Garmin’s sheets say that because water carries the sonar signal, the transducer must be in the water to work, and you cannot get a depth reading out of the water. Once the boat is in:

• Update the chartplotter software if your instructions call for it. Both the GT30 sheet and the LiveScope 2 instructions say you must update the Garmin chartplotter software when you install the device.
• Deploy the motor and confirm you have a steady depth reading and a solid bottom line. If the bottom looks tilted or the reading drops out, recheck that the transducer face is parallel to the bottom and that the narrow end points away from the propeller.
• Watch for noise. Garmin’s sheets tie interference to cable routing near other wiring, so a busy screen is a reason to look at where the cable runs before you touch the settings.
• For a live sonar transducer, check the view. The LiveScope 2 instructions say the chartplotter should default to an automatic orientation setting, which you can also set by hand from the sonar setup menu.
• After the first trip, look at the clamp and cable ties again. Recheck them any time the lower unit hits something.

Is a Trolling Motor Mount Right for Your Boat?

The Garmin Transducer Selection Guide lists the trade-offs plainly. On the plus side, a trolling motor mount gives sonar images from the bow, right below where you are fishing; it is easy to install and remove with no drilling into the hull; and it stores with the motor. On the minus side, the sonar image follows the trolling motor, which may not be the best direction in current or wind, and the transducer hangs low in the water, where it can hit submerged objects if you do not watch the depth.

That last point leads to who should look elsewhere: a trolling motor mount isn’t for you if you want depth readings while running on the main engine. When the motor is stowed, the transducer is out of the water and cannot read. If you need both, a second transducer on the transom or hull is one option, and hull placement follows different rules. Transducer types and other mount styles are covered in our Mounts & Transducers section, motors in Trolling Motors, and our method on How We Review.

Frequently Asked Questions

How do you mount a transducer on a trolling motor?

Fit the trolling motor bracket to the transducer, clamp it around the lower unit with the narrow end away from the propeller, set it parallel to the bottom, and tape or tie the cable up the shaft with a loop at the pivot.

Which way does the transducer face on a trolling motor?

For a standard transducer strapped to the lower unit, Garmin’s instructions say to point the narrow end, or front, of the transducer away from the propeller and to position it parallel to the bottom when the motor is in use. Live sonar transducers work differently: the view depends on the mount and how the transducer is positioned, as covered in the live sonar section above. Brackets differ between brands, so follow the transducer’s installation instructions for your model.

How do I mount a Humminbird or Lowrance transducer on a trolling motor?

Use the installation instructions and mounting hardware that came with that transducer, or the maker’s support site for your model. Brackets and clamps differ between brands and product lines, so the parts and steps above are Garmin’s and may not match yours. The general goals are the same: a secure clamp, the right orientation, and a cable that cannot be pinched or reach the propeller.

Will the transducer work when the trolling motor is stowed?

No. The transducer has to be in the water to read depth, so a trolling motor mount only works with the motor deployed.

About the author