Fish Finder Installation: An Easy to Follow Step-by-Step Guide

Man Installing A Fish Finder
Man Installing A Fish Finder

So you have done your research and bought a new fish finder that is perfect for your boat and annoyingly, before you can go out and use it, the next step is the fish finder install.

To install a fish finder you have to do one of the scariest things ever, in my opinion, drill holes in your boat. The last thing you want is to get the install wrong and drill more holes than necessary and end up with your fish finder not working properly.

Join me as I run through all the steps of fish finder installation, helping guide you through the process so you drill as few holes in your boat as possible.

How do you set up a fish finder?

Side Imaging Fish Finder
Side Imaging Fish Finder

Every fish finder, whether it’s a down imaging or a side imaging unit, works in the same way and thus requires the same basic install. You will need to:

  • Mount both the fish finder and the transducer in the appropriate locations on your boat
  • Connect the fish finder and transducer to each other and to a power source using the transducer and power cables provided

This is an incredibly basic version of the installation process as we have missed out all the fiddly wiring bits and cutting holes in your boat, but you get the idea.

Is It Hard To Install a Fish Finder?

Installing a fish finder can be very difficult or very easy and it all depends on how you want the fish finder to be installed and what kind of fish finder you own.

If you want a flush mount fish finder in your console, you’ll need to be good at using a jigsaw to cut the hole for it to go into. But if you’re using a binnacle mount, you just need to drill a few holes and you’re set.

If you need to do through-hull fittings for a through-hull transducer, you’re better off calling in an expert as a through hull transducer requires some very technical work – more on that later.

Transom mounted transducers on the other hand are very simple to install as all you do is screw them onto the transom, you’ll easily be able to do this at home.

Fish finder installation cost

Having your fish finder installed by a professional will cost a couple of hundred dollars, depending on their hourly rate and how tricky the installation is.

Bearing in mind that this is your prize offshore or bass boat we are talking about, it might be worth getting a pro in if you’re not confident about doing it yourself. This way your boat won’t get accidentally damaged during the process.

Where is the best place to mount a fish finder?

When it comes to mounting the fish finder display/head unit, you always want to mount it where you drive the boat from and in the easiest position so see it from. This might be either at the console next to the steering wheel or at the bow if you fish with a trolling motor.

It’s important to choose the right position for the display unit…

You will also have a few options when it comes to fish finder mounts and can either use a flush mount, a binnacle mount, or a third party mount. It’s important to choose the right position for the display unit and here is one of my articles that explains it in more detail.

Whatever mounting location you choose, make sure the fish finder screen sits at a height between your shoulder and waist on the console or near your knees or shins on the bow. This will make it much easier to see while you’re fishing.

How do you put a FishFinder on a boat?

To successfully put your fish finder on your boat, all you need to do is follow the steps and gather the tools and parts listed below.

Things You’ll Need To Install A Fish Finder

Hand Drill and A Box of Screws
Hand Drill and A Box of Screws

Here are all the parts you need to do basic fish finder install with, be sure to ready the fish finder’s manufacturer instructions first though and add any parts that might be needed.

  • Wire Fish Tape Tool
  • Gloves
  • Cordless Power Drill & Drill Bits 
  • Masking Tape
  • Heat Gun
  • Heat Shrink Tubing/Electrical Tape
  • The Bracket’s mounting screws and stainless steel nylon lock nuts
  • Cable Ties & Cable Wraps
  • Inline Fuse Holder & Fuse Kit / fuse block
  • Wire Stripper/Crimper
  • Crimped barrel connectors
  • Your Fish Finder Mount 
  • Transom Saver Block
  • Transducer Wires 
  • Transducer mount / transducer bracket 
  • Silicon sealant / adhesive sealant 
  • Jigsaw (flush)
  • Fish finder template (flush)
  • Manufacturer’s instructions

What gauge wire do I need for a fish finder?

​​When connecting the fish finder to your power source you shouldn’t use anything less than 16 or 14 gauge wire with a solid coating. This gauge is large enough to ensure the wire will not overheat and melt.

Connection Layout

The basic connection layout for fish finders is very simple as you will only ever need three wires coming out of your fish finder. The power will be run by two wires, usually a red for positive and a black for negative, that run to your fuse box or directly to your boat battery.

The other wire will be the transducer wire that relays the messages from the sonar waves to the display unit from the transducer in the water.

Cable Setup

black, red and yellow coated wires
Black, Red and Yellow Coated Wires

When setting up your cables you’ll need to drill an entry and exit hole for them to pass through from the fish finder to the power source and from the fish finder to the transducer.

When it comes to power wires, make sure they are long enough but without much slack, so trim them to adjust. Never ever cut the transducer cable as it will affect the performance of your fishfinder. Instead, leave any slack neatly tied with cable ties behind the display unit in the console.

How do you install a transom mount transducer?

Installing this kind of transducer is very easy as all you need to do is screw the mount onto the transom at the back of your boat and attach the transducer. But, you have to choose the right location and you have some options depending on your type of hull.


The transducer should be as deep as possible on the starboard side of your boat and at least 15 inches away from the propeller of your engine. This will ensure minimal disturbance and the best readings possible.

Mounting Options

You can either mount to a transom saver block and shield or directly to your hull (fiberglass only).

If your boat is aluminum then gluing a transom saver block to your transom is a must as you won’t have to drill any holes into your boat. I’d also recommend this for fiberglass boats as the less holes in your boat the better.


You can also add transom mounts directly to trolling motors and this is the easiest of all installs. You simply harness the mount to the trolling motor and add a wiring chase to keep the cabling tidy.

The Steps For Installing A Fish Finder

Step 1 – Register & Update Fish Finder Software

Garmin Fish Finder And Transducer
Garmin Fish Finder And Transducer

Before you put your fish finder on your boat you should first make sure it’s registered and that the software is updated.

By registering your fish finder, the manufacturer warranty and customer support will be enabled…

By registering your fish finder, the manufacturer warranty and customer support will be enabled, helping you fix it if something goes wrong in the future. It’s as simple as going to the manufacturer website and keying in your details along with the serial number of your fish finder.

To update the software you should use the manufacturer’s instructions. This might involve downloading new software onto a micro SD card and using the micro SD slots to update the unit or connecting it directly to a wifi network as many fish finders have wifi these days.

Step 2 – Find The Proper Location For Mounting Your Display

As we discussed earlier, make sure you have the right location chosen for your fish finder display unit.

Take into account the height and angle of the screen in relation to where you will drive the boat… 

Take into account the height and angle of the screen in relation to where you will drive the boat from so it is as easy as possible to see while you’re driving. You should also have decided whether you’re going to use a binnacle or flush mounting system.

Step 3 – Find Your Power Source

The next step is finding where the power source that is going to power your fish finder is located. This might be a fuse block or your cranking battery or a deep cycle battery if you’re running other power hungry marine electronics such as a live well.

Once you have found the fuse block or cranking battery you’re going to connect to, you can make sure your power leads will reach. You don’t want the unit’s wires to be too short or have too much slack.


Don’t lengthen or shorten the wires yet though, we’ll address that later on once the holes are drilled.

Step 4 – Drill Mounting Holes & Wire Holes

red and black cordless power drill
Red and Black Cordless Power Drill

This step differs depending on whether you have chosen to flush mount your fish finder or are using a binnacle mount, which is much easier. Whichever one it is, it’s time to start drilling holes in your boat.

Flush Mounting 

  • Stick your fish finder template on the console where you want your fish finder to go with masking tape
  • Draw a line around it with pencil 
  • Drill pilot holes, or a single pilot hole in one corner of the template outline that is big enough for your jig saw to fit through
  • Make sure to drill through masking tape and with the drill on full speed to ensure you don’t create cracks or splinters in the gel coat
  • Using the jigsaw on the highest template cut around the template outline
  • Drill the 4 mounting holes from the template
  • The space for your fish finder is now ready

Binnacle Mounting 

  • Place the mount where you want it to be
  • Using a pencil draw around the mount and mark the holes
  • Drill all the holes for the mount using the highest speed
  • Drill a wiring hole behind the mount with enough space for the wires to pass through
  • Drill an exit hole which will be exit point for both the power and transducer wires from the console
  • The space for your fish finder mount is now ready

Step 5 – Adding Sealant

Caulking gun with a black silicon background
Caulking Gun with a Black Background
  • Add sealant around all the holes you have drilled
  • Add sealant around all the edges you have cut if flush mounting
  • Add sealant to all the bolts you’ll be using to hold the fish finder in place
  • Do this before you have run the wires through the holes and before putting the fish finder in place


By adding sealant in all the areas you fish finder will stay in place a lot better, especially when in rough seas.

Step 6 – Run The Power Cabling

  • Take the power cables and run them from your fish finder to your cranking battery/fuse box 
  • Run them through the exit and entry holes you drilled in Step 4
  • Check to see if you need to shorten or lengthen the wires
  • If you need to lengthen the wires connect the same gauge and color wires using crimped barrel connectors for all electrical connections
  • To shorten use the wire cutters & stripper
  • Ensure the manufacturer’s in-line fuse remains intact
  • Leave the wires next to your battery and fish finder, do not connect them yet
  • Use cable ties to neaten up the wiring

Step 7 – Find The Location Where You’ll Mount Your Transducer  

Lowrance HDI Transducer
Lowrance HDI Transducer

We will only discuss mounting a transom mount transducer below as thru-hull transducers require drilling a big hole in the bottom of your boat, which you should only let a professional do

  • Before looking for your ideal transducer location read the manual and see what the transducer requires in terms of minimum depth submerged to function properly
  • Look at your transom and find the deepest spot with no intakes or jack plates nearby
  • Intakes or jack plates nearby will affect the unit’s performance
  • Take the transom mount bracket, quick release mount, and draw around it in the location you choose on the transom
  • Drill holes for the wires and the mount based on the template you have just drawn
  • You are now ready to run the wire

Step 8 – Running The Transducer Wire 

  • Take your new transducer wire and run it from the transom mount via the pre-drilled holes in Step 4 to the fish finder
  • Make sure it is a new transducer wire and not an old wire you are using
  • Make sure the running surface avoids all trolling motor wires or the engine’s wiring harness as it will cause electrical interference and poor readings
  • Do not trim off any excess wire, leave it neatly stacked behind the console
  • Do not connect it to the fish finder yet

Step 9 – Installing Your Transducer

Man Installing A Transducer
Transducer Installation
  • Connect the transducer to the wire
  • Cover the transducer mount outline generously with sealant and the bolts/screws
  • This stops water coming through the mounting holes and thus your boat sinking
  • Attach the mount and tighten the bolts/screws
  • Add the transducer to the mount
  • Angle your transducer at a right angle to the hull
  • You’re transducer install is complete


You can also use a transom saver block which is a plastic block you glue to your transom and then add the transom mount for the transducer to the block, thus drilling fewer holes in your boat. This is usually used on aluminum hulls but works with fiberglass hulls too.

Step 10 – Hook Up The System, Test & Install Fish Finder

  • Turn the battery off
  • Connect both the power wires and transducer wires to the fish finder
  • Turn the battery on
  • Turn the fish finder on 
  • If it doesn’t have power, check the wiring and fix it until it does
  • Seal up the wiring holes with sealant
  • Add more sealant to all holes, edges, or bolts if necessary
  • Install the fish finder mount or drop the fish finder in the flush hole
  • Screw in the bolts
  • Adjust the settings to read the transducer
  • Program the right sonar waves
  • Wait for the sealant to dry before launching the boat into the water 

Step 11 – Test Your FishFinder On The Water

  • Launch your boat onto the water
  • Turn on your fish finder
  • Adjust the sonar settings
  • Check your readings while stationary
  • Check your readings at 6 knots
  • Check your readings at 10 knots
  • Adjust the transducer angle as needed until you find the best readings possible
  • You want the transducer to be 90 degrees to the water line at fishing speed
  • Once you get solid readings, go and catch lots of fish and have fun

For additional tips and tricks when installing a fish finder, watch this video below.

How to Install a Fish Finder | Pro Tips and Tricks for All Models

Sounding Out

Thanks for reading my article, I hope you enjoyed it and found the instructions useful and are now confident in being able to install your own fishfinder.

Please share this fish finder installation article with your boating friends who might also want to take a look at it and check out some of our other fish finder articles, such as this Raymarine Dragonfly Pro review. We cover everything from installation to how to read a fishfinder.

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