What To Look For In A Fish Finder Before You Buy (Fish Finder Basics)

What To Look For In A Fish Finder Before You Buy

You’ve seen them for sale everywhere, and have watched many professional fishermen use them. Fish finders not only allow you to see where the fish are hanging out at, but also provide you with an enormous amount of other data from below the surface.

If you’re contemplating buying your first unit, or are upgrading from an older model, the following information should help you decide what to look for as you shop.

Fishfinder Basics

A fish finder is an electronic device that generates sound waves through the water column. As the sound waves travel through the water, those that hit a structure bounce back to the fish finder. These sound waves that have bounced back help to map the water, providing you with water depth, locations of underwater structures such as rocks and trees, as well as the location of fish.

Using Sonar

Sound Navigation Ranging, or sonar, was developed in the first half of the 20th-century. These devices interpret information generated through the vibration of sound as it bounces off of objects. Sonar has traditionally been broken down into two types:

Passive Sonar

This type of device does not generate sounds. It is simply a listening device, picking up on sounds from ships and aquatic animals such as whales. Passive sonar systems are often found in military or scientific applications.

Active Sonar

With this type of equipment, sounds can be transmitted and received. The sound that is emitted travels through the water until it touches an object or surface. The sound then bounces off of these and returns to the device, where it is registered as an echo.

Active sonar is used in fish finders, and the echos that it transmits and receives will help you to determine the depth, distance, and size of an object.

Active Sonar Components

Active sonar equipment will include a transmitter and a receiver. These components are placed next to each other in what is referred to as a monostatic operation. The transmitter generates a pulse, or ping, that travels through the water. As the echo from an object returns to the sonar, the receiver picks up the reflection.

An electronic transducer then converts that sound echo into light that is displayed on a screen. The display can be a flash, pixel, or predetermined icon that helps you to determine what these signals represent.

Different Types Of Fish Finders

Fish Finder vs. Combination Equipment

One of the first selections you will need to make is deciding what you want the equipment to do.

Stand-alone finder: Electronically, these are often the most basic units. A stand-alone provides you with information about water depth or locations of objects, such as fish, in the water column.

This type of finder may include a larger screen since they do not require space for other electronic packages. This type of product is often cheaper and is perfect for smaller boats.

Combination finder: These may also be referred to as a chart plotter. They will include GPS electronics along with the transducer used for locating fish. If you own a medium-sized boat, you may consider one of these as you can use the GPS to navigate on larger bodies of water.

Networked finders: These represent the ultimate electronics package. They are often Bluetooth/WiFi compatible and include a multitude of electronic packages. Packages may include radar/sonar, raster, GPS vector charts, satellite radio, as well as video equipment.

These products will tend to be the most expensive, due to their expandability and electronic packages included at the time of purchase. You will need more space to house a networked fish finder, and the required extra space works well for medium and larger-sized boats.

Fixed vs. Portable Equipment

Your next option to look into will be deciding on the portability of your equipment.

Fixed Position Fish Finders: If you own your own boat, you will probably want to look into a fixed position unit. The unit will be held more securely than a portable unit can. You will also be able to install the wires so that they are hidden (or at least out of the way).

Fixed position fish finders are often more solid in their design, and feature larger screens and control buttons and knobs. This will also increase the price of most units of this design.

Portable Fish Finders: The alternative to a fixed installation is the portable unit. If you are an angler who fishes from various boats, this will be your option. You can easily transfer your fish finder from your John boat to your larger Tri-Hull, for example.

Portable equipment will allow you to move the transducer around the hull of your boat as well. Anglers will often use portable fish finders for ice or shore fishing when they aren’t on a boat.

Another consideration is size, as many portable products will have a smaller footprint than a fixed-position unit of similar ability. This can also transfer to price, as many portable units will come with a smaller price tag.

A Closer Look At Transducers

Transducer Styles

Transom-mounted: This style uses a mounting bracket that is adjustable, with the unit hanging off or behind the hull.

Trolling-mounted: These are placed on the outside of the hull, or mounted inside of the propeller housing.

In-hull and Thru-Hull: These styles of transducers are mounted on the interior of the hull and broadcast signals through it.

Transducer Mounts

When looking at the transducer of your fish finder, the materials used for mounting is important to consider. Many transducers will come with a plastic transom style mount that can work with most boats.

For in-hull and thru-hull mounting, other materials will need to be used. Hulls made from fiberglass hulls will require plastic housings, while aluminum and steel hulls will benefit from steel housings. Bronze housings are available as well and work with fiberglass or wooden hulls.

Cone Angle

Manufacturers offer consumers a multitude of fish finders with varying sonar angles. The wider that an angle is, the more water you will be able to observe. This greater observable area comes at the price of sensitivity. While beam angles can be found between 9 and 60 degrees, most fish finders will use angles between 16 and 20 degrees.

Keep in mind that the deeper the water you are fishing, the wider your visible area will be. Also, all beams have a “dead zone.” This is a blind spot within the cone, often associated with a slope along the substrate.

Your sonar signal will register the highest point along the bottom but will not see the water in the lower portion of the slope. Dead zones will occur more often with a wider cone, so you can lessen the dead spots on your fish finder by selecting a smaller sonar angle.

Finally, you will want to keep in mind the specified angle compared to the actual sonar angle. The specified angle is the listed cone angle you are using. The signal sent from the fish finder actually covers a larger area, and signals outside of the specified angle may become visible is they are dense enough.

Beam Imaging Direction

Most traditional fish finders use a transducer that emits signals straight down into the water. They will often use lower frequencies, taking advantage of those signals traveling deeper than high frequencies will.

Another fish finder layout will broadcast signals sideways through the water. They will use higher leveled frequencies that produce more details. This style of beam direction is popular with shore fishermen.

Finally, there are units that generate signals in a 360-degree pattern. The higher price is justified by many, as users can adjust the angle from 10 to 360 degrees, as well as from all directions. This can provide a more accurate view of the water column.

Multiple Cones

Traditional fish finders made use of a single sonar cone, and products that still use this set up are economical entry equipment. Dual and triple cone systems will provide a more detailed underwater image, even if all signals are of the same frequency.

These signals may broadcast from the same image direction, or they might broadcast from more than one direction. More broadcasting components on the transducer will increase the price, obviously.

Another advantage of multiple cones is the width of your field of view. Multiple cones can cover a wider path in the water column, providing you with a bigger picture of what is going on under your boat.

Signal Frequencies

Many of today’s fish finders make use of multiple frequencies to provide underwater images. It is important to keep in mind that frequency rating will determine water penetration and detail of echo that is returned.

Higher frequencies, such as 192 or 200 kHz, will offer you a clearer image. These frequencies are ideal for shallow waters that are found in smaller lakes.

Lower frequencies are not as crisp, but they will penetrate deeper than a high-level frequency well. Many commercial fishing boats use equipment that broadcasts around 50 kHz, allowing them to image deeper water found in large lakes and ocean settings.

Usually, the higher the details a unit provides, the higher its price tag will be.

Other Fish Finder Considerations

Power Rating

The wattage rating of your equipment influences the type of water it should be used in. Lower ratings work adequately in shallow waters. The broadcast waves will not be as fast and the resolution levels are lower.

Higher wattage ratings are needed if you plan to fish deeper waters. If you want a highly detailed image of the water within the cone, you will want to consider a high wattage model as well.

Water Resistance Rating

You might be surprised to find out that fish finders are not necessarily waterproof. Each model or manufacturer will provide varying levels of water protection, with greater protection increasing the price.

If your fishing will include conditions where the housing will be doused in water, you will want a higher resistance rating than you would for a product that sits inside the wheelhouse of a larger boat.

If you are fishing from a kayak or tube, you will want to use equipment that has been rated to be submerged.

View Screen

Older fish finders may use black and white screens to display information, but newer models will usually have color displays. Colored pixels are easier to read in direct sunlight, and a larger array of colors can display more details. Obviously, color screens will cost more than a black and white display will.

Another consideration will be the screen resolution on the fish finder. Your screen will be rated on its resolution, which is measured in pixels. A pixel is a single dot on the display screen.

Greater detail can be observed with more dots, or pixels. The higher the pixel rating, the higher the price will be. Minimal screen resolution should be no less than 240 x 160 pixels. I would recommend your resolution be higher than this, however, as this rating will remind you of playing a video game from the 1980s.

Screen Features

Do not forget to look at the display before you buy a fish finder. Markings on the display will vary between manufacturers, as well as product models. All of the features in the world will not matter much if you have trouble reading the screen.

While most models have backlighting included, verify that it lights the screen to a level that you use in low and no-light conditions. If possible, I would suggest a backlight that can be adjusted and turned off.

Buttons and Switches

Another consideration is the buttons used for its operation. Oversized components are simple to activate will make switching between resolutions easier for you.

Also, the more you can adjust your fish finder, the more versatility it will offer.

Final Thoughts

Now that you know what to look for in a fish finder, and got the basics of how they work down, I’m hopeful you’ll be able to make a better decision when it comes time to finally buy one.

With that said, I’ve put together a few guides for some of my favorite fish finders based on different styles and for different situations. So be sure to check them out.

3 of The Best Fish Finders For Shore Fishing 

The Best 3 Fish Finder For Your Kayak

The Top Fish Finders For Your Pontoon Boat

Need A Battery For Your Portable Fish Finder? Check These Out

About the Author

When I'm not bass fishing or looking for steelhead in my home state of Oregon I can be found working on house projects dreaming of my next fishing adventure. I started this website to share just some of the things I've learned along my fishing journey, and the many things I'm still learning. Enjoy!