How To Install A Fish Finder

Technical Considerations

Degree of Difficulty

Moderate: You’ll need to know how to drill holes, connect wires with crimp connectors, run wires through your boat, apply sealant, secure wires, and more.  

Approximate Time

If you’re a seasoned pro, expect this project to take you about an hour. For those of you with little experience working on boats, expect the project to take you all afternoon. To have a fish finder installed professionally usually costs around $100, so if you’re not comfortable doing it yourself, it can be well worth it to call a professional. 

Tools

  • Power and/or impact drill
  • Jigsaw (optional)
  • Phillips-head screwdriver
  • Fish tape
  • Heat gun
  • Wire Stripper/Crimper

Materials

  • Hardware (washers, screws, etc.)
  • Inline fuse holder and kit (if not already attached to boat’s battery)
  • Masking tape
  • Cable ties/wraps
  • Silicone sealant/adhesive sealant (3M 5200 is recommended)
  • Crimp connectors
  • Terminal connectors
  • Shrink tubing

Project Cost

~$50, plus the cost of the fish finder (and any tools you don’t have)

Setup

The first thing you’ll need to do is examine your boat. Start by looking at the console of your boat. How much space do you have? What’s the best place to install your fish finder so that you’ll be able to look at it even when you’re behind the steering wheel?

 

From there, take a look at how your boat is wired. Some boats have pre-installed accessory power wires to make setup easy – on other boats, you’ll need to install the power wires and hook them up to your battery yourself. 

 

Look at the transom of your boat, as well. Many transoms have jack plates or other obstructions that you’ll need to work around when installing your transducer. 

 

Once you’ve got a rough idea of where you’re going to place your fish finder and transducer, it’s time to get the initial setup out of the way. Carefully unpack your fish finder, taking care to slowly uncoil the cables. 

 

Mount your bracket to your transducer using the hardware included. Finger tighten the screws, then use a power/impact drill to get them snug. You’ll also mount the mounting plate onto the bracket – here, you don’t want to fully tighten the mounting plate, as you may need to adjust the angle once you mount your transducer onto your transom. 

Step 1: Transom mounting the transducer

While you can opt for through-hull mounting, transom mounting is far easier to DIY, and it’s what we’re going to teach you today. For most boats, transom mounting is about as good as through-hull mounting – the only exception to that rule is boats with inboard engines, where through-hull mounting becomes a must.

 

To transom mount your boat, you’ll first need to find a spot deep on the hull with no obstructions: that means no strakes, no rivets, no jack plates, and no other obstacles of any kind. The goal here is to reduce water turbulence (which can affect readings), and to make the installation easier. 

 

The traditional method for transom mounting a transducer is to simply drill holes into your boat’s hull and mount the transducer directly to the boat. We’re going to show you a better way – using a transducer mounting board. Transducer mounting boards enable you to attach multiple transducers to your boat, and change transducers, all while only having to drill two holes into your hull. 

 

Transducer mounting boards (sometimes called mounting plates) are available for purchase at many marine stores and on Amazon – we’ve included a link to a board we like in the “Materials” section above. They’re easy to mount – simply place the board about ½” to ¾” above the bottom of the boat in order to mark your holes, remove the board,  then drill pilot holes (using a drill bit that’s slightly smaller than the screws you’re using to mount the board) where you want to attach the board.

 

Once your pilot holes are drilled, place your screws into the mounting board, then take marine-grade silicone and place it on and around your pilot holes. This ensures better adhesion, and will prevent possible leaks. With the silicone placed in and around the holes, take your mounting board, line up the screws to the pilot holes, then drill into the holes to attach your board.

 

With your mounting board attached, you can now install your transducer. In most cases, you want the transducer to be about ⅜” below the surface of the water at your optimal boating speed. Generally, this means it’s a good idea to install your transducer so that the bottom is about ¼” below the bottom of your boat – check your installation guide (included with the fish finder) to get a better idea of the optimal setup for your unit.

 

Your transducer will need to be installed horizontally. Press the mounting plate against the transducer mourning board, line it up so that your transducer is properly positioned, then mark your holes. Drill pilot holes into your mounting board, line the screws of the mounting plate up with the holes, then drill in. Note that because you’re using a mounting board, the screws that come with the fish finder may be too long. Swap for shorter screws if necessary. You should also note that, because you’re drilling into a board (and not the ship), waterproof silicone is not necessary for this step.

Step 2: Running the wires

This step is a bit ambiguous, because no two boats are exactly alike – and you’re going to need to take apart your boat to run wires towards your dash. Before we get into that, however, we’ve got to bring the transducer wires up from the bottom of the boat so they can connect to the control head (which we’ll install in the next step).

 

Running the wires up the side of your boat is fairly simple. The manufacturer should have included some clamps for your wires. Simply run the wires as taut as possible up the side of your boat, and use the clamps every 16 inches or so to keep the line taut.

 

The clamps, of course, need to be attached to the boat, and the process we used to affix the transducer mounting board applies here. You’ll mark the hole where you’re going to attach the clamp, drill a pilot hole, use a bead of silicone on the hole to ensure that it’s waterproofed, then use your drill to screw the clamp tight to the boat. Want a bit of extra waterproofing and security? Put a bead of silicone on the screw as well.

 

Once you’ve unscrewed hatches and compartments and opened up your boat (on some models, you may not even have to), you should be able to find rigging tubes (in most models) or other appropriate spaces to run your wires through so they don’t become tripping hazards. You’ll run your wires towards the dash, where you’re going to install your control unit. Here are a few tips:

 

  • This is the step where the aptly named fish tape comes in handy. When things are tight in your rigging tube, you can tape your transducer wire and power wire to the fish tape to pull them through the tube.
  • When possible, use a dedicated power cord for your fish finder, and wire it directly to your boat’s battery. This reduces interference, and makes troubleshooting a lot easier. If you have the space, run your power cord along a different rigging tube than your transducer cord to reduce interference. 
  • Use tape to mark your cords – you can do this by color-coding, or by writing on the tape with Sharpie. This helps troubleshooting, and can alleviate headaches if you start running a multi-fish finder setup. 
  • You may need to attach wire lengths together in order to reach the battery. To do this, use crimp barrel connectors – don’t solder. Protect connections with heat-shrink tubing.
  • You may need to drill a hole in the dash to run the transducer and power cables through. Double and triple check that there are no obstructions before drilling holes, and ensure that the hole is big enough for the cables. 
  • While you’re running the wire to the battery, you’ll still need an inline fuse holder/kit attached to the battery to avoid voltage spikes. 

 

Step 3: Installing your control head

When it comes to installing the control head – what many people consider to be the “fish finder” (though without a transducer it’s nothing more than a glorified GPS) – you’ve got a few options. Most units come with a gimbal mount, so we’ll start with that.

How to gimbal mount a fish finder

Gimbal brackets are incredibly easy to install. You’ll place the gimbal on an appropriate spot along your dash – if possible, right above the steering wheel is a great idea. Feel under the dash to make sure there are no wires or other obstructions that you’d rather not drill into. After that, you know the drill (pun intended) – mark your holes, pilot, silicone, screws, then drill into the dash. 

 

From here, attach your transducer and power cord to the back of the fish finder, then place the fish finder securely on the gimbal bracket. You should be able to swivel the bracket to get the perfect viewing angle – though we recommend playing with viewing angles before you start drilling holes.

How to flush mount a fish finder

 

Flush mounting a fish finder – that is, installing it directly into the console of your boat – is much trickier than gimbal mounting. There are a lot of advantages to using this method, however, the biggest of them being how dang good it looks. We recommend wearing a mask or respirator for this method, because things can get pretty dusty. 

 

The manufacturer will include a flush mounting template. Using masking tape, tape the template onto the section of the dash that you’re going to cut out. This is a “measure twice, cut once” scenario – and check as many times as you need to be absolutely certain you won’t be cutting into any wires or other obstructions.

 

To start, drill the four mounting holes that will be used to secure in your fish finder. From there, drill a large pilot hole at the corner of the template to fit your jigsaw into. Then, take your jigsaw and cut along the template to open the dash. Once that’s done, clear out any residue, then check to see if your fish finder fits in the hole you’ve made.

 

If you’ve been paying attention, you’ll know that the next step is applying silicone – all along the cutout, and in each of the mounting holes. Wire the fish finder, and test it to ensure that everything is working. Place the fish finder into the hole you’ve cut, then secure it with the hardware (screws and washers) they’ve included. 

Step 4: Testing it all out

Your transducer is secured, you’ve run all your wires up to your newly mounted fish finder, and you’re ready to take your new setup out on the water. Most of what we’ve done is fairly simple to reverse, so make adjustments if you need to. Enjoy your new setup, and happy fishing!

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