How to Choose & Use a Fish Finder

Written By: Dave Rush

A fish finder is a game-changing tool designed to help anglers maximize performance on the water. Technologies like down sonar, down imaging, side imaging, and forward-facing sonar (FFS) have revolutionized how we locate and catch fish. These tools allow anglers to read the underwater environment, navigate more safely, and make more informed decisions about where and how to fish. Whether you're a weekend warrior or a tournament pro, having a quality fish finder on board gives you a major edge.

A fish finder is an electronic sonar device that sends sound waves into the water and translates their echoes into images on a screen. This helps you detect fish, determine water depth, identify bottom hardness, and locate submerged vegetation or structure. Reading what’s beneath or around your boat is an essential advantage when fishing in familiar and new waters.

Fish Finder Characteristics

Power is one of the first characteristics to consider. The more powerful the unit, the stronger the sonar signal. This is especially important in deep or murky water, where higher power allows clearer and more accurate readings. The transducer is another vital component. It's the part that emits and receives sonar waves, and it needs to be matched to your boat and installation preference—mounted on the transom, trolling motor, or through the hull.

There are several types of sonar technology to choose from. Traditional 2D sonar offers a basic view beneath your boat, while down imaging provides greater detail that can resemble an actual photograph. Side imaging gives you a wider view of both sides of your boat, which is ideal for scanning large areas. More advanced systems use CHIRP sonar, which transmits multiple frequencies for greater detail and separation. Also, forward-facing sonar (FFS), one of the newest innovations, lets you see what’s happening in real time in front of your boat. It is great for pinpointing fish and watching how they react to your lure.

The screen is your interface with the water below, so its size and clarity matter. Larger screens—typically seven inches and up—make viewing and interpreting data easier, especially when using split-screen views to monitor multiple sonar modes at once. High-definition displays improve visibility, even in bright sunlight. A larger display is a worthwhile investment for anglers who fish often or use advanced features.  Some major electronics brands now offer units that are 20” and larger.

Many units also include GPS and chart plotting features. These tools let you mark fishing spots, navigate safely, and create custom maps of the areas you fish. Mapping features like AutoChart Live or Quickdraw Contours allow you to quickly see your data and return to productive areas with precision.

How to Use a Fish Finder

Once installed, getting started with a modern fish finder is relatively simple. Turn it on, choose a sonar view, and adjust settings like sensitivity, range, zoom, and brightness for your environment. Sensitivity determines how much detail shows up on your screen; too much can clutter the display, while too little may miss fish or structure. You may also want to toggle Fish ID on or off. Fish ID displays icons instead of raw sonar arches—useful for beginners, though experienced anglers often prefer interpreting the sonar returns themselves.

Understanding what you see on screen is key. Fish often appear as arches or dots, depending on the sonar type and settings. A hard bottom will appear as a bright, solid line, while a soft bottom appears faint or fuzzy. Vegetation shows up as clusters or vertical streaks. Side imaging displays fish as bright dots with shadows behind them, and FFS shows fish and structure ahead of the boat in real-time, even allowing you to watch how fish respond to your bait.

When choosing the right unit, consider your fishing style, budget, and boat setup. Entry-level models offer 2D sonar and GPS, perfect for new or casual anglers. Mid-tier and advanced models include CHIRP, down and side imaging, and even FFS compatibility for serious anglers. Major brands like Garmin, Humminbird, and Lowrance offer dependable models across all price ranges.

Equally important is how you install and protect your fish finder. A well-mounted unit ensures accurate readings and long-term durability. Use sturdy mounts—dash, gimbal, or trolling motor mounts should be stable and accessible. Transducer placement is critical. It must sit level in the water, away from turbulence, and be properly aligned. Poor installation leads to inaccurate readings and potential damage. Keep wiring neat and shielded from interference or weather damage and protect your display with a sun cover or screen protector when not in use.

Here’s a quick checklist to help you choose the right fish finder to fit your needs:

• Choose the right sonar type for your needs: 2D, CHIRP, imaging, FFS
• Match the transducer type and mount it to your boat
• Select a screen size that fits your space and visibility preferences
• Ensure it includes GPS and chart plotting if navigation is important
• Prioritize power output for deeper or dirtier water
• Make room in your budget for quality mounts and accessories
• Consider future upgrades like forward-facing sonar
  

Whether fishing shallow backwaters or deep offshore structures, a carefully selected and properly installed fish finder can transform your time on the water. Learn the features and spend some time dialing in your settings—and you'll be more confident, efficient, and successful every time you cast a line. All that's left is to put your new fish finder to the test at our top five freshwater fishing destinations or your favorite local spot.

Author's Profile: Dave Rush

Dave Rush is a veteran outdoor writer and photographer who has worked in the fishing industry since 2009. As Editor in Chief of Best On Tour, he brings over a decade of experience and a deep passion for telling the stories behind the sport.