Find More Fish

Here's how to install a bracket-mounted fish-finder and a transom-mounted transducer.

Anyone who enjoys fishing could benefit from the latest and greatest in fishfinder technology, but many small, trailerable boats don’t have room at the dash for full-sized flush-mounted electronics. And boats that use tiller-steering may not have a dash in the first place. Either way, the solution is a bracket-mounted fishfinder.

Using the bracket foot as a template, mark the spots for the pilot holes (1). We mounted a RAM Mounts D-111C-KNOB9H ball-joint bracket. Its large mounting plate includes a series of pre-drilled holes that will fit a number of different electronics units, including the Raymarine Axiom we’re mounting on this boat. Since our flush fiberglass mounting surface is backed with half-inch plywood, we’ll surface-mount the bracket using stainless steel screws. If you have access to the back of the mounting surface, through-bolts with nylock locking nuts are a better choice, because they are less likely to vibrate loose over time.

After marking and drilling, give each hole a dose of 3M 5200 Adhesive/Sealant. Hold the bracket in place. Before running in the screws, give each one a dip in more 3M 5200 (2), just to be sure the holes are well sealed and water intrusion isn’t a problem in the future.

Now you can use through-bolts to affix the fishfinder’s binnacle mount to the bracket mount (3). Then place the fishfinder on the mount.

The fishfinder, once in place, needs juice. Depending on what sort of boat you have and where you’re mounting the unit, this job can vary quite a bit, but the bottom line is you need to use a wire-fish to pull the power wire through a channel, or under the deck or gunwale, and to the battery compartment. Always start at the unit and fish the end of the cord that connects to the battery, not the other way around, because the plug end is bulkier and will be more difficult to maneuver through rigging tubes and other tight areas.

After you’ve run the wire, use a crimper (4) to crimp ring terminals onto the positive and negative leads. If the wire’s longer than needed for the application, coil up the extra and secure it with a tie-wrap or two.

Fishfinders don’t work without transducers, and where you place the transducer will have a big effect on performance. Locate an area at the base of the transom as far as possible from strakes, steps, through-hull fittings or other anomalies that interrupt the water flow and create turbulence (which interferes with performance) as the boat moves forward through the water. Also, locate the transducer so its bottom is positioned between 1/8 and 1/16 of an inch beneath the hull bottom. In the case of a 3-D or side-scanning transducer, such as the Raymarine Axiom 9, the transducer will need to be submerged from the center seam down, to maintain full functionality.

Once the transducer’s location is chosen, mark it and then tape on the manufacturer- provided mounting template. Note: Before you reach for the power drill, hold the transducer and bracket up against the template (5) to double-check the position. An error at this stage could lead to drilling additional holes in the transom. When you’re confident the positioning is good, drill the holes. Be sure to goop both the holes and the screws liberally with 3M 5200, prior to driving the screws in (6) and affixing the transducer in place (7).

Some transducer mounts, including Axiom’s, should initially be mounted with only two out of three screws. This will allow you to sea trial the boat and adjust the transducer up or down a bit as necessary, before driving in the third and final screw.

Secure the cable to the transom with a cable clamp or two — usually included with the fishfinder — to make sure it stays in place when the boat is underway (8).

As was true with the power lead, exactly where you run the transducer cable will vary from boat to boat. In any scenario, you will have to fish the thick plug-end through to the unit, because cutting and re-splicing a transducer cable causes additional resistance in the wires and can ruin the fishfinder’s performance.

Once you have fished the cable through to the fishfinder, coil any excess cable and secure it with tie-wraps. Then find any areas where the power and/or transducer lines are exposed for more than a foot or two, and where possible, use cable clamps or tie-wraps to secure them in place. Finally, hook up the power lead and connect the wires to the fishfinder.

Now step back, take a deep breath and admire your handiwork. But don’t go fishing just yet. That 3M 5200 needs a full week of drying time to fully cure.


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