After making a decision on choosing the right fishing kayak, you will be faced with another decision- what kind of depth finder to buy and how to install it? I kayaked fished for a couple years before going with any electronics and I really don't know how I got by without the use of a depth finder, I think that you are really at a disadvantage by not having a depth finder. A kayak and sonar work so well together-mostly because of the speed that we travel is always a perfect speed to be investigating the world underneath your kayak. For the purpose of this article we will refer to these units as depth finders even though they are refereed to as fish finders and they do locate fish. For me it is mostly about locating structure, drop-offs, certain bottoms and anything else that is likely to hold fish, even though there have been many times when I have seen the fish on the screen and the minute I got an offering to them I had a fish on.
Choosing the Right Unit for Your Kayak and Your Style of Fishing
There are a lot technical terms that should know when looking to buy a unit. Try to stay with one of the smaller sized units, space is limited on a kayak and I just like units that come in smaller packages that wont get in the way and clutter up your cockpit. Here are some different ways to mount a depth finder on your kayak.
Pixels: The number of pixels on a unit's screen determines how much detail it can show. Remember that pixels are arranged in columns and rows. The more pixels a screen has in each vertical column, the less depth each pixel represents and therefore the higher the resolution. The number of pixels in each horizontal row determines how long information stay on the screen before it scrolls off. So what does this all mean? Don't go too low with the number of pixels, and if you were going to very deep water, you might want to go even higher as the amount of pixels would be spread over a much wider area and therefore would not have as much detail. For example, if a sonar unit has 100 pixels vertically, with a range of 0 - 100 feet, each pixel is equal to a depth of 12 inches. A fish would have to be pretty large to show up as an arch at this range. However, if you zoom the range to a 30-foot zoom (for example from 80 to 110 feet), each pixel is now equal to 3.6 inches. Now the same fish will probably be seen as an arch on the screen due to the zoom effect. The size of the arch depends on the size of the fish - a small fish will show as a small arch, a larger fish will make a larger arch, and so on. Using a sonar unit with a small number of vertical pixels in very shallow water, a fish directly off the bottom will appear as a straight line separate from the bottom. This is because of the limited number of dots at that depth. If you are in deep water (where the fish signal is displayed over a larger distance of boat travel), zooming the display into a 20 or 30-foot window around the bottom shows fish arches near the bottom or structure. This is because you have reduced the pixel size in a larger cone.
Cone Angle: Most of the units that you will be looking at will come with a wider cone angle because most of the lower price units are made for shallower water. You will hear a lot of chatter about super wide beam, tri beam, dual beam and others-remember if you spread your cone too wide you will give up some detail and I feel that being able to accurately identify bottom contour is more crucial than maybe seeing a fish on the screen. A cone angle of 20 degrees will in most units be able to spread to 60 degrees with higher sensitivity settings. So a 20-degree cone is really a good bet and most of the units use this range. Keep in mind that some of the units that have some of the very large cone sizes (tri-beam) or side-finders will not work with a thru-hull transducer mounting application-the transducer needs to be in the water.
Power: Here again you do really don't have to worry about being underpowered, unless you are looking to explore depths of 200' or more. A unit with an output of 600 watts (peak to peak) or more will be fine for most applications.
Transducer: We are actually lucky here; we don't have the same considerations as boats; cavitations, hull rise, high speeds and hull compositions that rob your sonar of signal don't apply to kayaks. Even though most units come standard with transducers that are made for either a transom mount or a trolling motor, these will work fine as thru-hull applications with very little loss of signal-if any. So when shopping for a unit, don't think you need to get the shoot-thru transducer add on because the unit has come with a "transom mount".
Other Features: Look for a unit that is waterproof, you will get your unit wet and you will need something that will be able to hold up to the environment. If you are going to fish at night make sure it has a backlight feature. Even though many units have a temperature gauge built into the transducer, it wont be accurate if you mount it inside the hull-so it might not be an option worth paying extra for.
Portable vs. Non-Portable: Portable usually means that the batteries (most units will take 8 AA batteries) are contained in the unit and the transducer is of the suction cup variety, even though you can use the portable suction cup transducer and mount it inside the hull for a shoot-thru application. I have used the suction cup on the outside of my kayak and it is a major hassle with it catching everything from weeds to your fishing line, it also will add drag to you kayak and often will come lose. My advice is if you decide to use a portable unit, do it for ease of powering and use a semi permanent or permanent transducer installation on the inside of your hull-more on that later. When it comes to powering your unit I prefer the hard wired (12V battery) install over using the portable (batteries in unit), I just hated dealing with the batteries of the portable unit, I would only get 1 or 2 fishing trips and have to re-change (expensive unless you get a battery charger). A 12V battery-usually a small motorcycle or hobby model will give many days on the water, I will go out as many as 10 days before I even think about recharging it. I have had other people tell me that they have gone 20 fishing days without recharging their battery. There are only really 2 choices of amperage with 12-volt batteries, 4.5 and 7 amps. Here are the specs on a typical 12V 4.5amp battery Length 3.54 in, Width 2.75 in, Height 3.98 in. If you are going to run other accessories like running lights or a bait tank the 7 amps is the way to go.
Mounting Your Depth Finder: All units will come with a base and some even with swivel bases. You can use these if you have the required room for the base mount, if you don't have the surface area you might have to use another method like a Scotty or Ram-mount. You will have to take a little time to figure out where will be a comfortable place to view and to program your unit while on the water, you also should look at the placement of rod-holders and other accessories to see if they'll be in the way. I have seen some portable units mounted with just bungee cords but I like having it hard mounted. Most units have a power and transducer cable that will have to run from the unit (above deck) to inside the kayak hull, usually the transducer cable and the power are together but in some units they're separate, you will have to drill a hole in to run this cable and its usually requires a 1/2'" hole, if possible try to cover the hole with the unit base to lessen the change of water entering the kayak. If you have to plug the cable hole, you can try a small rubber stopper with a hole in it (for the cord).
Batteries: I touched on batteries a little but there are a few more points to remember; you will have to find a way to keep the battery sealed and it a good place in the hull, Tupperware works well and you will just have to find a place so it sits tight and won't bounce around. You will also need a charger for your 12 volt battery-make sure you get one with a shut-off, this will prevent overcharging the battery.
Batteries: I touched on batteries a little but there are a few more points to remember; you will have to find a way to keep the battery sealed and it a good place in the hull, Tupperware works well and you will just have to find a place so it sits tight and won't bounce around. A little cooler will also work great to hold the battery. There are also complete depth finder install kits available as well. You will also need a charger for your 12 volt battery-make sure you get one with a shut-off, this will prevent overcharging the battery. It is always a good idea to install the fuse link that is spliced into the positive cable, your owners manual will direct you how to do this-if it applies to your unit.
Here are some new ideas for batteries and this might end up being one of easiest set-ups for many fishing kayaks. Basically, its just a 8 AA battery battery holder and 9 volt snap connector, this will give the voltage you need, and with the new higher capacity rechargable batteries you can power most deptfinders for between 10 and 20 hours. You can purchase the AA battery holder and connector at Radio Shack for 3 dollars. Then it's just a matter of connecting it to the unit which can be done a few ways. Below we connected to the battery holder, and put it in a waterproof Otter Box, stuck it into the center hatch but can be put in Tupperware or a dry bag and put in the hull or anywhere for that matter.
Transducer Mounting: Over the years I have read about many different ways to mount a transducer, I will go over all the options there are. Remember to mount in a place that will be constant contact with the water, if you go to far forward you might be in an area that comes out of the water, therefore impacting the sonar signal. Whatever method you use, make sure you have the transducer's pointing straight down or you will lose the ability to show fish arches.
Suction Cup: This is a simple way to go but it can be problematic, since it is externally mounted and will catch everything from your line to weeds to about anything that floats. It also can come lose if the suction cup does not shape well to your kayak. If you have a unit with a suction cup it can be also mounted on the inside of the kayak and it will work thru-hull just as well, so there is no need for another to buy another transducer if you decide you want to mount it inside after buying a portable unit with suction cup.
Vaseline Method: Many have used just taken there transducer and popped it down on a dab of Vaseline and they're fine, a little duct tape also can help keep it down. I think this method is better used for maybe traveling where you want to bring your unit with you when renting a kayak. Also, this usually works best with flat hockey puck style transducers.
Semi-Permanent: I think more guys are using this method, basically it's just a piece of foam glued down to hull of the kayak with an area cut out to hold your transducer and keep it in contact with the bottom of the kayak. When it comes to gluing it down Lexel or Marine Goop works fine. The cut out for the transducer you should be tight so it fits snug. I use this method and it works great, sometimes I will have to place a little water in the cut-out so there is no air (transducers can't shoot thru air), another tip is use a little Vaseline inside the foam but water can also work as long as it stays on the packet, usually once you put it in there it stays there for a while and will insure a good reading. This set-up also gives you the ability to move from kayak to kayak whether using portable or non-portable.
Permanent: I have never used this method but many have with fine results. Going with either a 2-part epoxy or Marine Goop will work, some prefer to just use silicone because they want to be able to undue it when the time comes, the trick is to make sure you have a good mix of the and that there are no air bubbles. Most people will use a weight of some sort to put pressure on the transducer while it cures and this will squeeze the bubbles out. The obvious drawback here is that taking it off can be a hassle if you are changing kayaks or if you make a mistake in the setting of the transducer. Its a good idea to use some alcohol to clean both the transducer and the bottom of kayak so that the adhesive will work better.
Programming Your Unit: Most units will be ready right out of the box, but it is important to familiarize yourself with some of the features that you can control. If you are going to do any night fishing, you should know how to turn on the back light. Like discussed earlier the zoom is important because it can focus all the pixels on a section of the water column, for me its usually the bottom section of the water column I am more interested in. Sensitivity can be increase or decreased and usually this is done automatically in most units but sometimes you might have to tweak these manually to get the optimal reading. Once you learn all your unit has to offer you will be finding the fish on a regular basis.
Visit our Depthfinder Kit Page to see more pictures of how we rig depthfinders at the KFS shop.
As always if you have any questions feel free to call us at the shop 866-925-4537 or email us.