How to choose fish finders
Updated June 2026Independently researchedNo paid placement.
To choose a fish finder, first decide where and how you fish, a kayak angler needs different features than a bass boat owner. Focus on sonar type (traditional, CHIRP, or side/down imaging), screen clarity, transducer quality, and whether you want built-in GPS. Match the unit‘s power and frequency to your typical water depth, and set a budget that balances essential features with room to grow.
What type of sonar do you need?
The sonar type is the heart of any fish finder. Traditional 2D sonar uses a single frequency to show arches and bottom structure, it‘s reliable for most inland and shallow coastal waters, and it‘s what you‘ll find on budget-friendly models. CHIRP (Compressed High-Intensity Radiated Pulse) sends a sweep of frequencies for much sharper target separation, less noise, and better detail at varying depths; it‘s become standard on mid-range and premium units. If you fish complex cover like brush piles or rock ledges, side imaging or down imaging can be game-changers. Side imaging paints a wide picture of structure to your left and right, while down imaging gives a crisp, photo-like view straight below. Keep in mind that these imaging technologies require a specialized transducer, often sold separately on older units but included on most modern combos. For most anglers, a quality CHIRP unit with traditional sonar is enough, side imaging is a bonus for serious structure fishermen.
How much power should a fish finder have?
Power is usually stated in RMS watts or peak-to-peak watts, and it directly affects how deep you can see and how well you can separate targets in deep or murky water. A unit in the 200–300 watt range handles depths up to roughly 30 to 50 feet well, fine for many lakes and rivers. For reservoirs or Great Lakes fishing where you regularly fish beyond 60 feet, look for at least 500–600 watts RMS or higher; these mid-power units keep a clean signal at depth without dropping bottom lock. High-power units (often 1,000 watts RMS or more) are for serious offshore or deep-water anglers. They punch through thermoclines and keep target detail at 200-plus feet. But more power isn‘t always better for shallow water, in very skinny water (under 10 feet) a super-strong signal can actually clutter the screen. Match the power to your typical fishing depth, not the unit‘s maximum rating. In general, a 500-watt RMS unit is a sweet spot for most recreational anglers.
Transducer matters more than you think
The transducer is the part you mount on the hull or trolling motor, and it‘s arguably more important than the display. A mediocre processor paired with a high-quality transducer will give better detail than a top-tier screen with a cheap puck. Look for a transducer that supports the sonar types you want, some come as a single-skimmer that does both 2D and CHIRP, while others are dual-frequency or triple-frequency designs. The cone angle also matters: a wide cone (say 60 degrees) covers more water at shallow depths but loses detail deep, whereas a narrow cone (20 degrees) penetrates deeper with sharper returns. Mounting location affects real-world performance. A transom mount is easiest and works well for boats under 20 feet, but it can be damaged beaching or trailering. A through-hull mount offers cleanest readings at speed but requires a hole in the boat. For kayak or small-craft anglers, a scupper-mount or trolling-motor mount is common. If you fish varying depths, consider a unit that lets you adjust the cone angle or switch frequencies on the fly, many mid-range models now let you do that in software.
Screen size and resolution: what‘s enough?
Screen size affects how comfortable it is to read while running at speed or in bright sunlight. For a kayak or small jon boat, a 4-to-5-inch color display can be plenty, especially if it‘s high-contrast and sunlight-viewable. On a bass boat or center console, a 7-inch screen is the most common sweet spot, large enough to split-screen side imaging and GPS mapping without feeling cramped. Premium units go up to 12 or 16 inches, but those add weight and a few hundred dollars. Resolution (in pixels) matters more than inches: a 7-inch screen with 800x480 resolution will look grainy beside a 7-inch with 1024x768. For clear detail, especially when using down imaging or mapping, aim for at least 480 vertical pixels on a 7-inch screen, and higher on larger screens. Resistive touch is still common on budget models and works with gloves, while capacitive touch (like on a smartphone) gives smoother pinch-to-zoom but can be finicky in rain or with wet fingers. Test the glare and brightness in person if you can.
GPS and mapping: worth the upgrade?
Built-in GPS has become nearly standard on fish finders above the budget tier, and it‘s well worth the small premium. With GPS you can mark waypoints, track trolling routes, and see your boat‘s position relative to shore contours, useful even on small lakes. Basic GPS models show position and speed but lack detailed charts; they‘re fine for saving spots and navigating back to the ramp. More advanced units include preloaded coastal or inland maps, often with contour lines down to 1-foot intervals. If you fish unfamiliar waters or large reservoirs, a unit with integrated mapping (like LakeMaster or Navionics compatibility) saves you from buying a separate chart plotter. The ability to create your own depth-contour maps in real time is available on several mid-range and flagship models now, it‘s a huge benefit for building custom lake maps. Remember that GPS requires a clear view of the sky, so under dense tree cover or in canyons it can lose signal. Also, some units allow you to share waypoints wirelessly with your phone, which is handy for planning trips at home.
How to choose between brands like Garmin, Lowrance, and Humminbird
These three dominate the market, and each has strengths. Garmin is known for crisp screens, intuitive menus, and strong GPS mapping out of the box; their Ultra High-Definition sonar is especially good for clear detail in shallow to moderate depths. Lowrance has a long reputation for advanced sonar processing (especially their CHIRP and Active Imaging) and offers deep customization in networking and transducer options, a favorite among tech-savvy anglers who want to expand later. Humminbird is the leader in side imaging (they invented it) and their Mega Imaging series provides extremely wide coverage; they also integrate well with Minn Kota trolling motors for follow-the-contour features. Don‘t overlook Simrad, which shares technology with Lowrance but often comes in more rugged, marine-grade housings. For the average angler, the brand choice often comes down to which interface you find easier to navigate and which mapping ecosystem you prefer. All three have excellent customer support and plenty of owner forums. The best advice: pick a unit that fits your primary fishing style, for example, a Garmin Striker or Lowrance Hook series for budget all-rounders, a Humminbird Helix for side-imaging enthusiasts, or a Garmin ECHOMAP for cartography lovers. Consider the transducer that comes in the box and whether you‘ll want to upgrade it later.
Frequently asked questions
Can I use a fish finder in saltwater?
Yes, but you need a model rated for saltwater use. Most mid-range and above units are sealed against corrosion, but budget freshwater-only units can fail quickly in salt spray. Look for a marine-grade connector and a stainless steel or bronze transducer, especially if you plan to leave the unit mounted on a boat in coastal waters.
What is CHIRP sonar?
CHIRP sonar transmits a continuous sweep of frequencies (usually from low to high) rather than a single fixed frequency. This gives much better target separation, less noise, and more detailed bottom returns, especially in deep water or around submerged structure. It‘s now common on fish finders in the moderate price range and above.
Do I need side imaging?
Side imaging shows a wide picture of structure, fish, and bottom contours to the left and right of your boat, often up to 120 feet or more on each side. It‘s most useful when you fish large, featureless flats or need to locate isolated cover like stumps or rock piles. For casual or shallow-water anglers, traditional 2D sonar is usually sufficient.
What‘s the difference between a fish finder and a combo unit?
A basic fish finder shows sonar data only. A combo unit includes both a fish finder and a GPS chartplotter, often with mapping capabilities. Most anglers now buy combos because the GPS adds mark-and-return features and lets you combine sonar with navigation charts on one screen.
How deep can a fish finder read?
Maximum depth depends on power, frequency, and water conditions. A budget unit rated at 200 watts can typically read 30 to 50 feet, while a 500-watt model may reach 200 feet under ideal conditions. High-end units with 1,000 watts or more can exceed 500 feet. Always check the manufacturer‘s depth rating, and expect less depth in murky or salty water.
Should I mount a transducer on the transom or trolling motor?
Transom mounts are easiest to install and work well for most powerboats up to 20 feet. Trolling motor mounts keep the transducer in cleaner water at low speeds and make it easier to remove the unit for storage, but they can be vulnerable to strikes from debris. Kayak anglers often prefer a scupper hole or an arm mount that hangs over the side.