Skip to content
Sounder Choice Part One: The Basics

Sounder Choice Part One: The Basics

Sounder choice is a hotly debated topic amongst the offshore kayak fishing community. There are a number of different brands, sizes, features and mounting options to choose from which can make narrowing down and selecting a unit which will suit you a more involved task than you might think.

Here’s a little writeup on some of the most important things to know about sounders from an offshore kayaker's perspective regarding durability, effectiveness, value and ease of installation so that you can make an informed decision on what will work best for you!


Durability and Installation

It’s no secret that we subject all of our gear to an incredibly harsh environment and electronics are notorious for being one of the first things to submit to all of the surf, salt, sand and sun that we put them through. In any installation, it’s important to note that the primary areas where water tends to cause trouble are around the plugs and any connection that you make in your power cable as this is where corrosion will happen quickest. I won’t go into too much detail surrounding transducer mounts or how to do them here as there’s already plenty of information on that out in the interwebs. Have a look on some of the old kayak forums or feel free to get in touch with us and we can run you through it, but in essence, a through-hull (internal) mount is best for simplicity’s sake but will mean that you lose an accurate temperature reading, while an in-water (external) mount will give perfect clarity and readings every time without doubt but can be a pain in the proverbial. It’s also necessary for sidescan units.  

When done properly, an internal transducer install is highly effective and requires no effort to use once you're on the water.


The main two mounting methods which kayak fishos will use to protect their sounders from water and corrosion are:

  1.     A flush mount method which aims to keep plugs and connections inside the kayak and as dry as possible
  2.     A removable mount which will allow you to remove your sounder and store it safely (generally in a dry bag) inside your hatch during surf transits.


I am a big fan of the flush mount method when done correctly. It consists of cutting a hole in either a raised hatch lid or a flat section of the kayak in front of your seat and sticking it in place with sika-flex. Most sounders on the market nowadays have good waterproofing on front of the unit and this can be made the only point of contact with any waves or water by ensuring that the plugs at the back are well sealed whether they come with solid, waterproof connectors or you go down the route of using grease or some kind of sealant like silicone or sika-flex to keep the water out. One important bonus to note with this method is the fact that it’s in place and ready to go the moment you hit the water and get your rods out, but on the flip-side it’s permanent so if you’re looking to swap a sounder between a couple of kayaks this won’t be right for you.


Simple and effective, the flush mount can be used straight on the kayak or in a separate lid. The best part is, it's ready to turn on! 


The removable mount on the other hand can open up issues with certain plug types as it’s impractical to re-grease a sounder plug every trip and once your sounder is on and you’re paddling, that connection to the head unit will be exposed to splashes of water on all but the glassiest of days which makes it important to trust that no water will make it to the wiring or that your plug will take a knock and pop out. That said, the head unit itself when employing a removable mount won’t be bumping into sandbanks and copping full-force water jets in the surf zone when you inevitably get thrown off, so if you’re careful and able to keep the plugs dry and clean at all times this is a fantastic way to extend the life of your sounder.  It does also open up options for swapping the unit between kayaks if you’ve got a little creek basher that you want to chuck it on from time to time.


Provided that the plugs are up to scratch, this particular mounting method has its merits


To me, the maximum practical size for a typical workhorse kayak sounder is a 5 inch screen. Larger versions can be installed, but in my opinion are bigger than they need to be when you’re sitting so close to them and will restrict you to a removable mount. Bigger sizes are also generally a lot more expensive than their smaller brethren and the reality of this game is that no matter how well you care for your unit, it’s unlikely to last forever if you paddle semi-regularly so price should definitely be a key factor in your purchase decision.

4 inch units tend to be the standard choice, and for good reason. They tend to be cheap, simple and work perfectly well for finding fish and telling you the depth. I also personally don’t find that the GPS combo units that the split screen is too small to use effectively, but plenty of people will disagree there. Smaller units also draw very little power in comparison to larger screens, so you can generally get away with a small and cheap battery like a 2.5ah SLA if you desire.

SLAs are heavy and feature exposed terminals/connectors which corrode quickly and either need regular replacement or a bulky waterproof battery box for storage


With smaller and lighter weight lithium batteries like the FPV power range now available however, this certainly isn’t the biggest barrier to using bigger sounders on kayaks anymore. 5 inch units on the other hand sit in a nice in-between area on all attributes. They’re definitely big enough to see very easily and are quite well suited to a split-screen setup, but you won’t run into any space or weight issues when figuring out how to install them. That said, it’s more often than not a lot of money for an extra inch…


Sidescan, downscan and CHIRP

Here’s another hotly debated topic which not everyone agrees on, and that’s fine! It’s worth noting that there’s a lot of information out there on how these different sounder types and modes work and it’s too much for this article which ideally won’t go on for too much longer! If you’re keen to check out more, have a search around on google or head to a couple of these pages for a wee bit of insight:

In the meantime though, here are some of the implications for each when you’re rolling around offshore in your stealth.

Sidescan and downscan (names differ amongst brands) basically give you a very refined, picture-like reading of what they see. Sidescan, as the name suggests, shoots out to the sides of the transducer on a very wide angle and gives you a picture of what’s happening well out to the sides of your kayak.

Its major downside is that it restricts you into installing the transducer externally which reduces the simplicity of your setup— something that I personally value highly.


You'll need to get a bit fancier with transducer installation if you're set on sidescan


Downscan on the other hand functions more or less as standard sonar by showing what’s beneath you, but with a much more refined image quality. The issue with both is that they can both struggle to give the super clear image-quality returns that they’re intended for when they’re not being used on flat water. In an ideal situation with no rocking or rolling when you’re moving forwards at a slow pace, both of these can throw up some pretty awesome readings and it’s often possible to easily pinpoint what type of fish you’re seeing, not just where they’re sitting or approximately how big they are. I used to have a hummingbird 798 and recall on a few distinct occasions being able to see the difference between bass and yellowbelly on a still day at Bjelke-Petersen Dam which was pretty awesome. If you have a look at marketing material for these units, you’ll likely see plenty of barra, threadies and sharks all showing up perfectly clearly, but take note that these images will have all been taken in environments with a good amount of perfectly flat water. Upon using that same hummingbird offshore, I was finding both sidescan and downscan much less useful. Both modes still separated fish from clutter very well, but I found that I often missed smaller patches of fish compared to standard sonar. In only 20m of water and a moderate chop there was definitely no defined shape to the returns. What I will say in their defence however is that they’re fantastic for telling exactly what type of bottom you’re fishing over, even in less than perfect conditions. Rocks show up as rocks, weed shows up as weed and reef shows up as reef. A lot of people with newer and more powerful sidescanning units have been also loving them, so it’s definitely worth noting that my opinion and fishing style isn’t the only one out there. If you’re going to value the chance of seeing things show up out to your sides (or fish in still water) enough to justify the extra money that you will need to spend to get your hands on one of these, then it’s going to be worth further consideration.


CHIRP on the other hand is a feature that I’ve found to be highly valuable. It essentially has the same display as standard sonar and works well in the relatively shallow waters that we fish, but it offers a marked improvement in target separation without any notable loss in being able to see things that you will want to. Put shortly, if a fish is sitting on top of a rock it will, more often than not, show an arch on top of a blob instead of one big blob. Can recommend.


Hopefully this has given you a bit of a rundown on what features to look out for and think about from an offshore kayaking perspective. Next week, I'll run through and weigh up some models from the more popular brands available. 

Tight lines and happy fish-finding!


Owen Gray 




Previous article Sounder Choice Part Two: The Options