Complete Guide to Understanding Fish Finders & Using Them Effectively

Modern technology has put the old rod and reel instinct for fishing in the back of the boat and brought the fish finder technology into the 21st century.

Because their popularity is growing so rapidly, so too are the technical features of these handy tools for fishing. Here is a comprehensive guide to how to use it, and what to look for before you make an investment in one. I hope this guide will help you find the best fish finder that satisfies your needs and is within your budget.

With each product on the market today, there are many different variations of features to choose from:

Greyscale vs Color Fish Finders

You can buy one that is in color or is in black and white, called grayscale. For color options, the stronger that the echoes return to the transducer, then the darker the color that is displayed. Color will give you more depth definition and will help you to be able to determine more easily what type of fish is being displayed on the screen. For black and white displays, as the pixel count increases then the resolution will improve.

Screen Resolution (aka Pixels per inch)

It goes without saying that the more pixels that your model can offer, then the better resolution you will get. A contributing factor to pixel performance is the contrast, which must be sharp for the pixel quality to be optimal. Always go for a fish finder with maximum vertical and horizontal pixels on the screen.

Fish Finder Display Sizes

Screens come in sizes ranging from less than 4” to 10” displays. The larger the screen the more information is displayed at one time like the GPS and split-screen viewing etc. Fishfinder display sizes are something that you really need to think about in terms of what your fishing needs are and how much information you want to be displayed at any given time.


The power of the sonar frequency must be considered in any product that you are considering depending on how you intend to use it. Just like any other product that is energy supplied, the more powerful the wattage the faster and better the quality. So, if your model has optimal wattage, the sonar waves are faster and an image will be created more quickly. This is especially true at large depths. That means if you intend to mostly use it in shallow bodies of water, then you will do fine with a product that gives you only a low wattage.

Sonar Frequency

The main component of any model is the sonar coupled with the transducer to produce images of fish and other objects under water. There are different frequencies to consider depending on where you fish and the type of boat you are using to mount the transducer.

  • Higher frequency: A transducer that has a higher frequency will have a greater amount of wave cycles per second. This is important for identification of smaller fish, especially in shallow depths.
  • Lower frequency: This has the opposite result with less detail, but it is better for identification of larger fish. Lower frequencies also have a greater capacity of energy for further below the surface of the water.
  • Dual frequency: This type of transducer has a crystal component that allows for vibrations from more than one frequency.

Transducer Use and Your Boat

Each model comes with a different type of transducer that is designed with varying cone angles that work better on certain types of boats:

  • Fiberglass hulls work best with an in-hull mount
  • Transom mount transducers are best for planning hulls that are not more than 28 ft.
  • Hull mount transducers work well on sailboats for less drag
  • External transducer mounts protrude from the hull and will need a fairing block accessory for best results in order to aim the Sonar beam. Best when used on un-trailered boats of a larger size.
  • The wider the angle of a transducer cone, the more area is being covered by the beam.
  • The deeper the water, the more sensitive the beam becomes and it diminishes in quality

Transducer cones are available in ranges of 9 degrees to greater than 60 degrees. A typical transducer is between a 16 and 20-degree angle. The best angle for you if you plan to fish in a variety of depths of water would be a 20-degree cone angled transducer.

Side Imaging

Just make a mental picture of your model’s screen folded right down the middle. Then mentally fold it at the base of the water column. Anything that is on either side of the boat will be displayed as a bright object with a dark shadowy shape. Long shadows mean taller objects are present. Anything that is right under the boat will show up in the water column. You can see how side imaging works with animation in this video:

Down Imaging

This type of image has been equated to the same as having a glass-bottom boat and being able to look directly down into the water. It is made up of very high-frequency waves that slice through the water and creates a very clear image of what is under your boat. You can also get an idea of what down imaging looks like at after having a look at this video:

For more detailed comparison, check out this guide on side imaging versus down imaging.

Installing the Fishfinder

We have written a step-by-step guide on installing a fishfinder on your kayak or boat with some tricks and tips. Please check that out.

Also, after properly installing it on your boat/kayak you should keep it clean and protect it from earthly elements.

Types of Fish Finders

Fish finders can be divided into different types based on their functions and some extra but important features.


This is a solid and economical choice if you have a modest-sized vessel and fish mostly on inland lakes. It gives an effective display for simply scouting out what is around you when you are fishing.

GPS Combo

The GPS combos work well on boats that are medium-sized and want to have some navigating component as well. The GPS and sonar can be displayed at the same time, or each component can be used by itself.

an ice fish finder


These are units with all the bells and whistles. They are data friendly with GPS, radar, video, and also SiriusXM radio.

CHIRP (Broadband)

This broadband version can typically emit much lengthier pulses that will give you up to 50 times more pulse energy. So, the “pings” that it creates will pulse through the water at differing frequencies bringing back images in much greater detail.


These are for anyone who is on a fishing vacation and wants a model that is easy to transport. They come with the display unit, a mounting part, transducer, and a battery all in a pouch or case.

The latest portable fish finder version is called a castable. This actually floats in the water and is controlled by an app on your phone through Bluetooth or Wi-Fi.

Ice Fish Finder

Most of these units use flashers and display a graph of what is happening below. Some ice fish finders are flashier types that will show a real-time view as well.

Common Techniques Used in Reading Fish Finders

These are some techniques that you can use to understand your fish finder properly.

The depth of water

It will be displayed in meters and feet on any fish finder model. How accurate the reading will depend on the model you are using. You can also find a depth sensor very often on the transducer component. Depth gives you an indication of the types of fish that are in that body of water.

Speed sensor

This is your fish finder speedometer tool. Speed is an important element for using a fish finder, so it is a good idea to note your speed at all times. Some products do not perform as well at a higher rate of speed because of how the sonar waves are emitted. Try the product at varying speeds and note the quality of the imaging.

Reading the display

  • Information has to be read from the right side to the left side
  • The far right side of the display screen shows more recent images
  • Darker colors mean there is a stronger echo being emitted
  • Thick lines are a sign of harder structure underneath the boat
  • Some models show raw data while others convert the raw data into fish icons using Fish-ID technology featured on newer models
  • Sonar waves are displayed
  • Cast out several times to test your fish finder model, then make a note of what you found to reference on a later trip. This should including noting the depth at which you found the fish.


This tool will help you to keep track of where you are and where you need to go. Additionally, it will give you the depth of the water and the structural makeup beneath the water. This is great for keeping track of fishing spots that have been exceedingly good. The chart plotter lets you plot the course each time you want to head out to that specific spot and can even create a trail around particularly treacherous underwater structures.

Try to use a split-screen image with one side for finding fish and the other for chart plotting. If you opt for a combo model, then it both tools will work in concert with one another. It will actually let you go back to look at an area that was recorded and save the GPS coordinates.

fish finder split screen view


If you are in shallow water, use a zoom component to take a look at up to the final 10 ft. of water so you can capture the type of underwater contours are in the area. This gives you a great idea of the types of fish in that particular spot as well as warm and cold pockets of air for different schools of fish. This will not work in a large depth of water since the contour of the bottom is not as important.

Don’t use a high frequency in water that is extremely thick with algae. The false readings will make up the majority of what you see on your display and lead to a very unhappy and frustrating fishing trip.

Manufacturers to Consider

Garmin, Lowrance, Humminbird are some of the best-known fish finder makers to us. But there are a few others who manufacture good ones at an affordable price. Do consider products from these producers before making your mind.

Garmin Fish Finders

The Garmin manufacturer has displays that you can read with ease with a backlight component. It has a battery recharge unit included with most styles, and it connects the right transducer.

Lowrance Fish Finders

This company has an HDS series that has a feature that lets you “drive” your boat through an object that is being rendered on the map. This is great for seeing the valleys and peaks under the water as your boat moves. They have also recently introduced a more affordable CHIRP broadband called the CHIRP Elite.

Humminbird Fish Finders

They are known for listening to the consumers that buy their products and adapting their product to suit their needs. They recently introduced what they call the Helix Series that features a lightweight, portable new product.

Raymarine Fish Finders

With a version that can transmit on at least 60 frequencies, it will give you an LCD screen image of anything under the water as you can probably get and be able to hone in on specific types of fish.

Furuno Fish Finders

The Furuno dual-frequency fish finder has unique technology only this company can offer. It is called RezBoostT which will give you optimal resolution and more ease in separating your target by as much as 8 times any other product.

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