Choosing The Right FishFinder – A Definitive Guide

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How to Choose the Right FishFinder

FishFinders are devices that help you find fish, these devices help remove all the guesswork, thus making it easy for an angular to find fish. And today, there is what we like to call the Sonar wars where we have various types of fishfinders from different brands like Garmin, Lowrance, Humminbird, Furano, Simrad, and Raymarine. As a result, if you’re looking for a fishfinder that suits your needs, it’s not entirely easy as you can get lost in all the many series these brands have to offer. This is a comprehensive guide that takes away all the hard parts, I have done a lot of research on these devices, and this post will help you understand what to look out for when looking to buy a fishfinder, and of course, the best fishfinders available today from the big names in the marine industry.

Origin of Fish Finder

In 1948, two brothers Kiyotaka and Kiyokata who were owners of a small marine electrical company in Japan developed a device for detecting fish underwater. The tool was developed using scrap materials, it didn’t perform well as expected initially, but the gradual development of the fishfinder led to the successful finding of fish. Years later, Lowrance, who died at the age of 80 and has been called “the father of modern marine electronics” after founding Lowrance Electronics, invented a fish finder in 1957.

Today, there are various types of fishfinders with different capabilities and for different types of environments. There are fishfinders for freshwater, saltwater/deepwater, and coastal water fishing.

What is a FishFinder?

A fishfinder is a SONAR system that helps an angular locate schools of fish underwater. This device works based on the Sound Navigation and Ranging (SONAR) system. It consists of a transducer that converts electrical impulses from a transmitter into sound waves and sends them down the water. When these waves hit an object such as fish or a bottom structure, some of these waves are absorbed by the object while some are reflected back to the source, the transducer then vibrates and causes some voltage fluctuations that are amplified and interpreted by the fishfinder system with the end result showing a 2D or 3D representation on an  LCD or CRT display.

Over the years, the marine industry has witnessed ground-breaking technologies that help angulars find and catch more fish. Today, there are high-end CHIRP Sonar fishfinders with built-in GPS, Radar systems, and Chartplotters that serve both recreational angular that want the best result and of course for commercial angulars.

Components/Parts of a Sonar Fish Finder

The average Sonar fishfinder consists of three main parts; the Sonar fishfinder system, the transducer, the display, and in some cases for high-end fishfinders, a GPS.

  1. The Sonar Fishfinder
  2. The Sonar system is the main part of a fishfinder. It’s a sounding system that was initially used to locate objects underwater and measure distance. Its the responsibility of the fishfinder system to interpret vibrations from the transducer and show the result on the screen of the fishfinder. When reflected ultrasonic waves hit back at the transducer, it vibrates and causes minute voltage fluctuations that are amplified by the fishfinder to show an image representation on the fishfinder display.

  3. The Transducer
  4. The Transducer is the main part of a SONAR fishfinder.  A transducer is simply a device that can convert any form of energy into a readable signal. In the case of a fishfinder system, first, the transducer vibrates when a voltage is passed through the Sonar system, thereby emitting ultrasound waves in a specific frequency. These frequencies appear like a beam with a cone shape below the water surface. When these waves strike an object say a fish or bottom contours, some of the waves are absorbed by the object, while some are reflected back to the transducer. When the reflected waves hit back at the transducer, it will vibrate and causes a fluctuation in voltage. This voltage fluctuation is interpreted by the Sonar system and displayed on the screen.

  5. The Display
  6. The display of a Sonar fishfinder is a very integral part of the system. Voltage fluctuations caused by a vibrating transducer as a result of reflected waves from the water are interpreted and shown on the display allowing the angular to read and understand what is going on under his boat. Various types of display technologies are used on modern-day fishfinders such as LCD and CRT with LCD being a standard in modern fishfinders.

    The average Fishfinder can show you the speed of your boat, the depth of the water below your boat as well as a representation of both current and past history of fishes that have crossed the beam scope covered by your transducer.

  7. GPS/Chartplotters
  8. Garmin GPSMAP 8616xsv Chartplotter/GPS fishfinder

There are high-end fishfinders that have inbuilt GPS for navigating waterways, waypoints, and contours. Some fishfinders with built-in GPS also take it a step further to include a Chartplotter that gives angular access to full-color maps of lakes and coastal waters. These Chartplotters allow the angular to get a clearer picture of his current location, thus making it easy to target specific spots for fishing while also being able to find your way back home effortlessly. For instance, the Garmin GSP series feature BlueChart® g3 which contains detailed maps of coastal waters as well as LakeVü™ g3 which contains a detailed map of lakes in the US. In other words, a fishfinder with Chartplotter gives the angular superior control with regards to location and route tracking. It makes it easier to target specific areas for fishing.

How Does a Sonar FishFinder Work? – Mechanism of a FishFinder

A simple representation of how a fishfinder works
The way a fishfinder works is very straightforward. First, a piezoceramic disc which is the main physical device inside a transducer vibrates as a result of voltage passed through it from a Sonar fishfinder system, these vibrations which occur at specific frequencies send out ultrasonic waves underwater in a diverging manner continuously in a cone shape. Thus, any object within the area covered by the beam can cause interference with the waves. The object absorbs some of these waves while some are reflected back to the source, the transducer.

When reflected waves hit back at the transducer, it results in vibrations that cause voltage fluctuations which are picked up, amplified, and interpreted by the Sonar system, the fishfinder system thus displays the result which includes 2D or 3D graphical representations of the school of fish as well as the speed of your boat, water depth and temperature of the water.

The velocity of the ultrasound waves from the transducer travel at 1500meters/secs and there are various objects that can interfere with the waves ranging from the seabed, school of fish, debris, or even air bubbles. The larger the object, the greater the reflected wave, and also the clearer the picture you see on your screen.

Types of Transducers – Choosing the right transducer

Like we mentioned earlier, a transducer is at the heart of a fishfinder system. It’s the transducer that sends out the ultrasound waves underwater and when these waves hit an object a reflection occurs in form of an echo back to the transducer. When reflected waves hit back at the transducer, it vibrates and causes fluctuations in voltage which is interpreted by the fishfinder system with the end result, an image on your screen. There are various types of transducers offered by the biggest brands in the industry and we will try to classify them based on their features.

  1. Based on Frequency
  2. Transducers can be classified based on the available frequencies. You have the Standard traditional transducer that’s built on a dual-frequency system and has to alternate between 50kHz and 200kHz and the CHIRP Sonar transducers that feature multi-frequencies.

    • Standard Transducer
    • Standard transducers are what you find on castable fishfinders as well as other medium-sized fishfinders. This type of transducer is a single-element transducer that contains a single piezoceramic disc that vibrates alternately at 50kHz and 200kHz. The lower frequency has a wider scope(Beamwidth) and can be used to target schools of fish in deepwater. While the higher frequency has a smaller scope and can be used to target schools of fish in shallow water. A frequency of 200kHz can be applied for precision, it gives a clearer picture than 50kHz, but has a shorter wavelength as a result the reach is limited, while a 50kHz frequency has a longer wavelength and can travel deep into the water up to 1000ft or more.

    • CHIRP Sonar Transducers
    • A CHIRP (Compressed High Intensity Radar Pulse) Sonar is what you find on mid-range to high-end fishfinders like Chartplotter/GPS combos. This type of transducer covers a wide range of frequencies and as a result, it can show you fish and objects that standard transducers won’t. A CHIRP Sonar can have frequencies ranging from 15kHz to 200kHz. Basically, A CHIRP sonar is a multi-frequency transducer in which separate elements vibrate at their respective frequencies. As a result, this type of transducer can vibrate from a low to high frequency continuously. This allows for greater clarity and picture quality. While the high frequencies can help you target objects in shallow waters, the low frequencies can help you target objects in deep waters in the clearest form possible. Garmin’s Panoptix series is a CHIRP transducer that offers the best clarity underwater that can help you target a school of fish in both shallow and deepwater.

  3. Based on Mount Style
  4. Transducers can also be classified based on the type of mounting style. Transducers can be mounted in four different ways; transom, thru-hull, in-hull, and trailing motor mount.

    • Transom Mount
    • A transom mounted transducer
      Transom mount is the most widely applied method of mounting a transducer. This method allows you to mount a transducer outside the boat hull. It offers the least signal loss and also offers a way to easily adjust the transducer after installing it. When mounting a transducer using the transom method you have to take into considerations water turbulence, distance from the propeller, and as well the transom angle. It is recommended that the transducer is placed a few distances from the propeller and slightly away from the center of the hull, this helps prevent water turbulence, while the required transom angle is specified by the manufacturer.

    • Thru-hull mount
    • A thru-hull mounted transducer
      Another method of mounting a transducer is the thru-hull method. This method requires that a hole is drilled through the hull. This method requires that you mount the transducer at a location with minimum deadrise where it can continuously be immersed in water. The best location to mount a thru-hull transducer will be the aft midship as close to the centerline of the boat as possible. When mounting a thru-hull transducer, you have to ensure that it’s clearly separated from other transducers, rivet lines, or other objects that might create turbulence.

    • In-hull Mount
    • An in-hull mounted transducer
      The in-hull method of mounting a transducer also know as shoot-through transducers do not require drilling a hole through the hull. Rather, the transducer is glued to the hull. This method can only be applied to fiber-glass boats since fiberglass has similar sonar characteristics as water and thus allows the passage of Sonar signals with minimal loss. For the Sonar signals to pass through the hull, the hull must be a single layer construction. Some of the advantages of an in-hull transducer are that the transducer is free from damage, no drilling of the hull, no obstructions, and you can also get the best possible signals even at very high speed. However, with this method, the signal depth is limited and this method can’t be applied for side-imaging transducers.

    • Trailing Motor Mount
    • A trailing motor mounted transducer
      Some transducers can be mounted on the trailing motor. These types of transducers are mounted on the underside of the trailing motor and also oriented in the direction of travel of the trailing motor. For rectangular-shaped transducers with directional bias, the transducer is mounted on the underside of the trailing motor with it facing away from the propeller.

      Transducer Materials

      Transducers are available in various materials ranging from stainless steel, plastic, and bronze. If you’re mounting a thru-hull transducer, you want to ensure that you mounting the transducer on the recommended hull material to help prevent dangers as a result of molecular reactions.


  • Transducers with bronze housing are recommended for fiberglass or wood hulls. Never install a bronze housing in an aluminum hull as it will electrolytic corrosion to occur.
  • Transducers with plastic housings should not be used on a wooden boat. Wood swells as it absorbs water, so it may crack the housing.
  • Transducers with stainless steel housing are compatible with all hull materials. Its recommended for metal hulls to prevent electrolytic corrosion provided that the transducer is isolated from the metal hull.

Choosing The Right Frequency – Scanning With The Right Frequency

A traditional/standard transducer will have a dual-frequency build that alternates between two frequencies which in most cases is 50kHz-200kHz. This type of transducer has lesser clarity compared to multi-frequency transducers. When greater quality is required, a CHIRP Sonar which offers a wide range of frequencies offers far better clarity and targeting than traditional transducers. Some frequency options in a typical transducer will include the following;

  • Low CHIRP (25-80kHz) or 50kHz: Lower frequency which means maximum depth penetration for deep-water fishing. And for the greatest depth with a traditional 50kHz transducer, choose a sounder with 1-2kW of power.
  • Medium CHIRP (80-160kHz) or 83kHz: This gives the widest coverage area which is ideal for watching under your boat in shallow water.
  • High CHIRP (200kHz): A higher frequency offers better clarity with a higher image resolution. This makes it easy to be able to separate between a fish and a structure especially for fishes hiding under a structure.
  • 455kHz will allow you to scan an area with picture-like images as can be seen with Garmin Sidevu and Clearvu.
  • 800kHz allows for even better picture quality than 455kHz but has a lower depth penetration.

Types of Sonar FishFinders

There are various types of fishfinders ranging from compact castable fishfinders to high-end fishfinders with CHIRP sonars and Chartplotter/GPS combos.

  1. Castable/portable fish finders
  2. Deeper Smart Sonar Pro+ 2 fishfinder
    Castable fishfinders are the most portable of all fishfinders. These are very compact and portable fishfinders that work wirelessly with a smartphone. This type of fishfinder is cast into the water and you can easily view the readings of the signal from your connected smartphone. Castable fishfinders are used mostly by recreational fishermen for shallow water and ice fishing. Some of the best castable fishfinders on the market include iBobber, Deeper Smart Sonar Pro+ 2, Garmin Striker cast, and Fishhunter by Lowerance’s FishHunter Pro.

  3. Traditional Sonar Fishfinders
  4. Traditional Sonar fishfinders can be referred to as fishfinders that still utilize the dual-frequency system and can sometimes have inbuilt GPS for location and route tracking but lack Chartplotters and CHIRP Sonar.

  5. Fishfinders with CHIRP Sonar
  6. Garmin Striker Vivid 4cv fishfinder
    Due to the high clarity of CHIRP sonars, a majority of fishfinders on the market are designed with a CHIRP sonar built-in. This type of fishfinder offers great clarity that allows the angular to find and catch fish that a dual-frequency transducer won’t show you. And for cruisers, a CHIRP Sonar can help you locate objects that might appear hidden from a traditional fishfinder. Some of the best fishfinders with CHIRP sonar include the Garmin Striker and Striker Vivid series that come with both Sidevu for displaying objects to the side of the boat and Clearvu for displaying objects below the boat.

  7. CHIRP Sonar FishFinders with Chartplotter/GPS Combo
  8. Garmin GPSMAP 8616xsv Chartplotter/GPS fishfinder
    For commercial fishermen as well as deepwater cruisers, fishfinders with CHIRP Sonar and Chartplotter/GPS combo offer a more comprehensive experience that allows you to locate objects underwater with the best possible clarity as well as sail effortlessly with total control. This type of fishfinders has a CHIRP Sonar that allows you to target objects in both shallow and deepwater, a Chartplotter that gives you access to the best locations to fish and sail, and a GPS that allows you to track your routes and locations. The best fishfinder with Chartplotter/GPS combo are the Garmin GSPMAP and ECHOMAP series, Simrad NSS EVO3S and GO series, Raymarine Axiom+, and Axiom Pro Chartplotters, and more from Lowrance and Humminbird.

How to Read a FishFinder

How to read a fishfinder

The transmitting ultrasound waves from a transducer are reflected as echos by objects such as fish, seabed, debris, or any other object that falls within the beam scope of the transducer. The reflections cause the transducer to vibrate resulting in a small voltage fluctuation that is amplified and interpreted by the fishfinder and displayed on the screen as fish arches and seabed.

On average, fishfinders have yellow, orange, red, blue, and white colors. Some models of fishfinders can have more colors, but the good thing is that you can always customize your preferred colors. To read a fishfinder is very easy going by what you see on your screen.

  1. Yellow color is the strongest signal and represents seabed, bottom, big fish, or anything that is very large
  2. Red color is in-between. It also indicates a big signal like the yellow color, but less strong.
  3. Blue color is the weakest return, it can mean that the object is very small or almost out of the beamscope of your transducer.
  4. White color means no return.

The very first thing you should always do is to turn on the A-scope of your transducer. This allows you to see what is directly under your transducer. It means what is happening right now, and of course the best signal.

The very intense bright yellow color you see at the bottom represents the bottom of the water, it’s the solid seabed. This can have a mix of red and blue which represents a less solid bottom.

If the transducer is setup correctly and moving at 4-5miles per hour, you should see arches. Fishes look like arches when the boat is moving and they look like long worms when the boat isn’t moving. That’s because the fish remains right under the transducer beam scope for a longer time.

A yellow color arch is a great signal that indicates that the fish is right within the scope of the transducer, while multiple yellow arches indicate the school of fish. When a fish appears blue, it can mean that the fish is almost outside the beam scope of your transducer, this also applies to red arches.

Data shown on an average fishfinder include the frequency of the transducer, the temperature of the water, the depth of the water, the speed of the boat, and more.

FishFinder Brands

There are many brands in the marine industry making some of the best fishfinders on the market. Some of the popular brands include Garmin, Lowrance, Furano, Humminbird, Raymarine, and Simrad. These brands have series of fishfinders ranging from the standard fishfinder to the high-end Chartplotter/GPS combo. Garmin Striker Vivid series and GSPMAP and ECHOMAP UHD series are some of the available fishfinders with Chartplotter functions from the brand. Lowrance HDS live and Hook Reveal series are some of the collections from the brand.

Newer brands like Deeper Sonar and iBobber make some of the most popular castable fishfinders you will find on the market. This includes the Deeper Sonar series and the iBobber series.

FishFinder Checklist – FAQs

When choosing a fishfinder there are lots of questions to ask, but here we will look at the most common questions. The basic factors to take into consideration are where you’re fishing, boat type, and material. This will help you choose the right fishfinder and transducer.

  • How much power do you need?
  • The power of a transducer ultrasound wave is expressed as watts RMS (Root Mean Square), it’s the power at which the transducer sends ultrasound waves underwater. Greater power means greater strength and by extension, greater depth in water. In this regard, a transducer with a 1KW – 2KW power rating is ideal for deepwater fishing while a transducer with 200W – 1KW will serve well for coastal water, lake, and any form of shallow water fishing.

  • How much frequency?
  • A standard fishfinder will have a dual-frequency transducer that alternates in most cases between 50kHz/200kHz or 77kHz/200kHz. While a CHIRP sonar will have a range of multi-frequencies which allows for higher penetration underwater for better clarity. You can use a 50kHz frequency to scan a large area around your boat, then you a 200kHz frequency to target a specific area for greater precision.

  • What fishfinder is right for shallow water fishing?
  • If you’re fishing in a lake or perhaps in coastal waters, a standard fishfinder will make a great choice. You can also extend your search to include castable fishfinders. Standard and castable fishfinders are also the best fishfinders for kayak owners. Like we mentioned earlier, standard fishfinders can come with a dual-frequency or in some cases CHIRP sonars as in the case of the Garmin Striker Vivid series. For lake and coastal water fishing, a fishfinder with 200W to 1kW (RMS) will serve.

  • What fishfinder is right for deepwater fishing?
  • Angulars and commercial fishermen fishing in deepwater will require a fishfinder with higher power (RMS) and a CHIRP sonar for better clarity. Fishfinders with Chartplotters/GPS are great additions. A transducer with a power rating of 1KW and above is an ideal choice for saltwater fishing as it allows for great sonar depth and with CHIRP sonar, you can see objects clearly. The Garmin ECHOMAP and GSPMAP series are some awesome options to choose from.

  • Does the sonar come with a transducer or sold separately?
  • Another factor to consider is if the fishfinder comes with a transducer or the transducer is sold separately. Many fishfinders like Chartplotters don’t come with a transducer. The transducer is sold separately. While castable and standard fishfinders come with a transducer.


    In conclusion, the secret to catching more fish starts with choosing the right fishfinder for your preferred environment. Also, mounting the transducer properly is also a big factor. Choosing the right fishfinder, the right transducer, properly mounting your transducer, and scanning with the right transducer will help you catch more fish. And with extra tools like a GPS and Chartplotter, you can track your routes, locations, and sail effortlessly.

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