Kayak Fish Finder Installation Guide

10/11/2019

A handy guide covering the essentials of choosing a fish finder and installing this to a fishing kayak. This guide takes a detailed look at fish finder technology, mounting a fish finder to a kayak, the different ways to fit a transducer to a kayak and the options for powering a fish finder. Install a fish finder to your kayak and start catching more fish!

There is no doubt about it, having a fish finder on a fishing kayak is a game changer. It gives you an insight to the world beneath your kayak, which would otherwise be largely unknown. Find reefs, drop-offs, gullies, plateaus, sand-banks and other fish holding features. Tell the difference between soft ground and hard ground. Know the depth you are fishing in, the water temperature and if there are any fish showing within the water column beneath the kayak. The information provided by a fish finder will ultimately allow you to fish more effectively and result in more fish to the kayak! Some may say it's cheating but most of us are in the kayak fishing game to catch fish and if there is a device that will put you onto more fish then it's a worthwhile investment!

Fish finders as standard are designed for use on boats and a little head scratching is often needed to fit one to a kayak. Luckily there are several ways to go about it with off-the-shelf accessories to make fitting a fish finder to your kayak much easier.

Which Fish Finder for your Fishing Kayak?

Lowrance, Garmin, Raymarine and Humminbird all produce fish finders with models to suit the occasional user to the hard-core angler. A standard entry-level unit will have a 4-inch colour display and use broadband sonar to show the bottom structure and any objects within the water column. Some models also include basic GPS plotting functionality allowing you to add your favourite fishing spots and launch marks to a simple base-map. These units are what the majority of kayak anglers will opt for as a first fish finder and at the time of writing the Lowrance Hook2 4x GPS and Garmin Striker Plus 4 are popular choices. These units can be found in the £100-150 price range here in the UK.

Fish finder prices increase as they become more feature-rich with larger displays, DownScan Imaging, CHIRP Sonar and GPS chart plotting functionality. Larger 5 and 7-inch screen sizes allow you to study the detail on screen more easily, and are useful if you are using a split-screen mode e.g. showing sonar readings beside a GPS chart.

DownScan Imaging offers a higher resolution of the seabed structure than is possible with standard sonar and is great for locating fish-holding structures. CHIRP (Compressed High-Intensity Radiated Pulse) sonar uses a pulse of sonar at varying frequencies to provide a more detailed reading of the seabed and any fish within the water column. This provides a clearer image and better target separation making it easier to distinguish between individual fish, large fish and bait shoals.

A reef revealed using Downscan Imaging

Shoals of fish revealed using CHIRP Sonar

GPS chart plotting functionality allows the user to view their GPS position and this can be used to plot marks, tracks and routes onto a base-map. This has obvious benefits for marking features or productive fishing spots and drifts so that you can return to them. You can also see your speed over ground and bearing which is also useful for navigation. Base maps can be upgraded to highly detailed seabed charts, such as those from Navionics, providing the user with incredible detail of the ground in their vicinity. This makes navigating to marks that look productive very easy.

GPS Chartplotter display on a Raymarine Dragonfly fish finder

A GPS chartplotter with upgraded Navionics+ Sonar Chart basemap

GPS information is also plays a role in staying safe on the water - you can navigate yourself to the shore or your launch mark should you find yourself in fog, you can see that you are making ground against adverse conditions, know when you are drifting at a speed or direction that may cause trouble, and see your GPS position clearly incase you need to relay this in an emergency.

Fish finder units with 5+inch displays, CHIRP Sonar, DownScan Imaging and GPS chart plotting with upgraded Navionics+ charts will set you back over £500, but you will have an incredible source of information at your disposable whilst fishing on your kayak! Popular units with such specification include the Lowrance Hook2 Combo models, Raymarine Dragonfly Pro series and the Garmin EchoMap series.

Whichever fish finder you opt for, allow at least an extra £50 for accessories you will need to fit it to your kayak.

A selection of popular fish finders for kayak fishing

Installing a Fish Finder to a Kayak

There are three main parts to consider when installing a fish finder to a kayak:

Where to mount the main head unit?
Where to fit the transducer?
Where to store the power source for the unit?

Some kayaks, including models from Viking Kayaks and Feelfree Kayaks, come with dedicated removable fish finder / sonar pods offering a complete mounting solution for the head unit, power source and transducer.

Lowrance Hook2 5 fish finder fitted to the Viking Kayaks Tackle Pod

The Viking Tackle Pod offers a removable fish finder installation solution

Viking Kayaks Tackle Pod transducer recess

The Viking Tackle Pod features a recess beneath to house and protect a transducer

The Feelfree Sonar Pod offers a removable fish finder installation

Many kayaks do not have this luxury and a little thought is needed before fitting a fish finder. Each model of kayak will differ in how it is best to install a fish finder and the main ways are explained here.

Fitting the Fish Finder Display to the Kayak

All fish finders will come with some form of mount. It is a matter of finding a suitable flat spot on the deck to fit this – ideally in a position within easy reach such as on a centre console or on the side of the foot-well. On some kayaks this is not possible with the supplied fish finder mount as the footprint is too big. There are several after-market fish finder mounts that offer much smaller footprints making them easier to install to a kayak.

Universal and model-specific mounts are available from Scotty and Railblaza and Ram Mounts. These accessory brands also offer track mounting options to allow for fish finders to be fitted to the slide tracks found on many fishing kayaks, for easy installation and easy removal at the start and end of a session. My own Raymarine Dragonfly 5-Pro is mounted to the slide tracks on my kayak using a Dragonfly-specific mount and a Quick-Release Track Base from Ram Mounts.

I particularly like the Ram Mount options as the system uses ball and socket technology for almost infinite angle adjustment of the display, allowing you to get the perfect viewing angle.

Railblaza Fish Finder Mount for Lowrance Hook 2 on a kayak

Railblaza Mount for Lowrance Hook2

Ram Mount for Raymarine Dragonfly

Garmin Echomap fitted to a kayak using a Ram Mount fish finder mount

Ram Mount for Garmin Fish Finders

Fitting a Fish Finder TransduCer to a Fishing Kayak

Here things get a little trickier. The transducer is the component that pings the sonar through the water column and picks up the return signal. The unit then uses the time between transmitting and receiving the signal and the strength of the return signal to generate the on-screen information. There are several ways to fit a transducer to a kayak and it will very much depend on the model of kayak as to which method is best employed.

Scupper Mounted Transducers

Some kayaks come with moulded-in recesses under the hull specifically designed to house a transducer. You will have to check compatibility if your kayak has such a recess as transducers vary widely in size and shape. A specialised mount is available from Lowrance, which allows a transducer to be fitted to a scupper hole on a kayak. Whilst designed for Lowrance transducers, it can be adapted for other brands.

Hobie offer a transducer scupper mount for Lowrance fish finders across most of their range. The so-called 'Lowrance-Ready' system consists of a transducer scupper recess with protective cover, along wth a series of cable seals pre-fitted to the hull to make fish finder install easy. Hobie’s latest cutting edge design for 2019 is the Guardian Retractable Transducer Sheild, providing a further level of protection by allowing a transducer to retract into the hull when not in use. Scupper mounting offers full water contact for a perfectly clear transducer reading.

Lowrance Scupper Hole Transducer Mount

Hobie 'Lowrance-Ready' Transducer Mount

Hobie Guardian Transducer Mount - Retractable

Hobie Retractable Guardian Transducer Mount

Arm Mounted Transducers

Transducers can be mounted to arms that extend over the side of a kayak. Scotty, Railblaza and Ram Mounts offer kayak specific transducer arms, which will accept all the major brand transducers.

They all work off a deck or slide track mount which the arm attaches too, reaching over the side of the kayak and down into the water. The Ram Mount transducer arm is very good as it consists of a soft alloy arm that can be bent and shaped to match the side profile of your kayak for a neater finish.

Arm mounting a transducer offers full water contact for clear readings, however you can experience some drag whilst paddling/pedalling with a transducer arm deployed.

Scotty Transducer Arm fitted to a kayak with a Garmin Striker Plus 4

Scotty Transducer Arm mounted on a slide track

In-Hull Transducers

It is possible to bond many transducers against the inside hull on a kayak. The transducer will shoot sonar through plastic and composite kayaks with minimal loss of reading clarity. This will not work with more complicated side-scan transducers, but for standard sonar / downscan transducers, this method works fine. To bond a transducer to a kayak, you will need to encase the transducer in a suitable adhesive which will give a strong hold to the plastic or composite surface. Flexible adhesives are preferable as they are less likely to 'pop off' the surface if the plastic flexs. I recommend Sikaflex EBT+ Clear, but others use adhesives such as CT1 or if you can get hold of it, E6000 or Marine Goop.

You will need to make a ‘transducer well’ from a piece of high-density foam – a gardeners kneeling pad works well. Cut out a rectangle of foam that is approx. 60-80mm longer and wider than your transducer. Draw around your transducer allowing a 10mm gap around its outer edge. Cut out this shape from the foam. This will need to be glued against the inside of the hull, on a flattish area roughly on the centre line, and allowed to dry to form a sealed well. Inside the bow hatch usually offers enough space and easy access to do this. It usually pays to scratch up the area on the inside of the hull where you will stick this so that the glue has a rough surface to bond too.

You can then fill the well approx. 2/3rd's full with your chosen adhesive. It is important to ensure there are no air bubbles trapped within the glue, as these will cause sonar reflectance. If bubbles are present, use a thin sharp instrument to scrape these to one side or out of the glue. Once clear, the transducer can be firmly pushed down into the glue and against the hull of the kayak. Leave the kayak and transducer level and allow the adhesive to cure, which usually takes 24-48 hours. Once cured the sonar will be able to shoot through the solid glue and kayak hull without issue. If air bubbles have found their way beneath the transducer these will usually show as vertical white lines of interference on the display when on the water. If this is the case, the transducer will need to be removed, glue peeled off and the process started again.

In Hull Transducer Installation with Marine Goop

A transducer installed inside the hull of a kayak using an adhesive

With the transducer installed inside the kayak, you will need to run the cable up to the main unit on the deck through a waterproof cable gland. Scanstrut and Hobie offer various size cable seals that are perfect for the job.

A Lowrance Hook2 4 fitted to a kayak with a Railblaza Hook2 Mount

A Scanstrut Cable Seal fitted to a kayak providing a waterproof wiring option into the hull

Hobie 3 way Cable Seal fitted to a kayak for fish finder wires

The Hobie 3-Way Thru Hull Fitting allows up to 6 cables to pass through the hull!

Powering a Fish Finder

Fish finders will run off a 12V power supply and the most practical power source on a kayak is a battery. Rechargeable Sealed Lead Acid (SLA) batteries are most popular, and are available in various sizes. A 12V 7Ah SLA will power most units for a couple of sessions before charging is required and these batteries can be brought for around £20. Some larger more demanding units will need a larger battery of 10Ah or more. Use a simple 12V trickle charger to recharge these batteries, which can be found for around £20.

A 12V 7aH Sealed Lead Acid Battery is suitable for most fish finders

Store the battery inside a dry bag or waterproof box to keep your power source dry. Whilst a waterproof battery box requires a little DIY to put together (click here for a guide to make one), a simple 5L roll down dry bag is sufficient to keep a battery dry on-deck on in the hull of a kayak. Simply place the battery into the bag and position the power lead to one corner of the opening. Gently roll down the top of the bag several times to form an overlapping seal and clip the bag latches together to hold the seal in place.

Most kayakers opt to store the power source on the inside of the kayak, running the power cable up to the main unit through a waterproof cable gland. If an in-hull transducer install has been used then both the transducer and power cable can be passed through a single cable gland such as a Scanstrut DS30-P Medium Seal.

You could also store the battery box or bag on the deck - if you choose this option then ensure that the box or bag is secured well to the kayak incase of capsize!

Dry bag for fish finder battery on a kayak

A simple roll top dry bag will keep your battery dry on the kayak. Secure to the deck or place within a hatch.

A waterproof battery box to power a fish finder

A DIY dry box for a fish finder battery. Place this within the hull for more protection

Eyes Beneath Your Kayak

With a fish finder installed your fishing kayak will become a much more effective platform, allowing you to use the data displayed on the screen to inform your fishing locations and fishing tactics. Drop your bait at the right time, cast your lure over the right spot. Fish finders are now readily available to the kayak angler, and are easy to use. With a little thought and a few accessories they can easily be fitted to a kayak. A fish finder will certainly give you an edge on the water and having eyes beneath your kayak will only help to improve your catch rate!

A shoal of mackerel showing on Donscan Imaging mode on a fish finder

A shoal of Mackerel in midwater

CHIRP Sonar and Downscan Imaging on a Raymarine Dragonfly 5 Pro

CHIRP Sonar (top) and Downscan Imaging (bottom)

Where To Buy?

If you are in the UK, there is no better place to source all your fish finder essentials than Cornwall Canoes - specialists in kayak fishing! Check out their website for everything needed, from the fish finder to the battery and transducer mounts...