How we compare

Where the specs come from

Every spec on a product page (part number, screen size, screen resolution, built-in sonar, marine network ports, nmea 2000, transducer connector, thrust, shaft length, voltage, dimensions, weight, water rating) is a claim we recorded with its source: the page it was read from, how it was read, and the date. The product page shows the source next to each value, so you can check it in one click.

Sources rank in this order:

1. The brand's own material: its product page, spec sheet or product feed.
2. A store's listing of that exact part number, when the brand doesn't publish the figure.
3. Anything else, such as a search result or a figure worked out from the source's own numbers. These values are marked with an asterisk.

Within a rank, a page read directly beats an archived copy of it. When a store blocks automated reading, we read the copy the Internet Archive keeps instead, and the source says "archived".

Of the 1,712 spec values shown on the site right now, 99% come from the brand, 1% from a store. Another 0% are carried over from the original catalogue and haven't been re-checked yet. Those are labelled not re-verified wherever they appear.

When sources disagree

The highest-ranked source wins, and among equals the newest reading wins. A value carried over from before we kept sources ranks below everything, so any checked reading replaces it.

When two good sources disagree by more than measuring noise (half an inch or 3% on a dimension, 5% on a weight), we look at both and mark the wrong one rejected, with the reason. Rejected claims are kept rather than deleted, so the next check doesn't pick the same wrong number up again. 20 claims have been rejected so far.

A few conventions make products comparable:

• Screen size is the diagonal in inches. Where a brand gives only the width and height of the display, the diagonal is worked out from them and marked as derived.
• Network ports count the Ethernet ports (Garmin Marine Network, Ethernet) that live sonar and unit-to-unit sharing plug into. NMEA 2000 is counted separately: it does not carry sonar.
• Dimensions are length × width × height in inches, as the brand publishes them.

Confirmed, inferred, unconfirmed

Every product carries a confidence label. It's computed from its sources, never typed in by hand:

• confirmed (163 products): the part number and every shown spec were read from the brand's or a store's own page, spec sheet or feed, or an archived copy.
• inferred (96): read the same way, but at least one value rests on a search result or a figure worked out from the source's numbers, or the product has no part number to pin it to.
• unconfirmed (29): at least one value hasn't been re-checked since the catalogue began. The product page says which.

Prices

Prices are re-checked every week. Each price shows the date it was seen and the store it was seen at. The headline price is the cheapest store that has the product in stock. If no store has a price, we show the brand's list price, labelled as such. A price we haven't been able to re-check reads "recorded <date>, not re-checked since", never as current.

Some large stores refuse automated price checks. For those, we look the part number up by hand and record the price the store's own listing shows. When we can't do that, the store is listed without a price rather than with a guessed one.

Size tiers

Brands name sizes differently: one brand's "large" is another's "medium". The size filter (compact, medium, large, XL) places each fish finder by its screen size within its own family. We rank it against its family-mates, or an editor places it. Tiers are for narrowing a list, so the screen size is always shown next to them.

What works with what

Each answer is one row in our data: an add-on (a live sonar system or a trolling motor), a fish finder or a whole family of them, what is being asked (does the add-on's sonar show on the unit, or does the unit control the motor), and a verdict:

• Works the brand lists the pairing.
• With adapter it works through a named cable or module.
• Conditional only with a minimum software version, or on some versions of the product.
• No the brand says it does not work, or (with an asterisk) the unit is missing from the brand's own complete list.
• Not published no source we have read answers it. We don't guess.

Sources, best first: the brand's own compatibility list (Garmin publishes one per product), its help-centre articles (Humminbird and Minn Kota), and its spec pages (Lowrance's list what each display works with). The quoted sentence is kept with every stated answer and re-checked against the page. A model's own row beats its family's row, so "all HELIX G4N" can be refined to "only MEGA SI and MEGA DI models".

A No* is worked out, not stated: no live sonar or motor maker lists another brand's displays, so a unit absent from a brand's own list is marked no, with that list as the source. When a brand adds a unit to its list, the next weekly refresh picks it up.

Discontinued products

Products a brand no longer sells new stay in the catalogue, because people buy them used and need to know what still works with them. They're kept out of every comparison, listed under legacy & discontinued, and each one names what replaced it. 147 products are listed there now.

How the site makes money

Some "buy" links are affiliate links: if you buy through one, the store pays SonarMatch a commission at no cost to you. Those links say so right next to the button. Affiliate status never decides what we list, the order things appear in, or which store a price comes from. The headline price is the cheapest in-stock store, whether or not we earn from it. No brand or store pays for placement.

What we don't do

• No scores or "best" picks. A single score hides whose priorities set the weights. We show the numbers and the sources, and you decide.
• No hands-on testing. Specs and compatibility are the brand's published statements, not something we tried on a boat.
• US market only. Part numbers, prices and availability are for US stores.
• No guessing. A value nobody has published is left blank, not estimated.

What the terms mean

Built-in sonar

What the unit decodes on its own: CHIRP (traditional 2D sonar swept across frequencies), down imaging (Garmin ClearVü, Humminbird Down Imaging, Lowrance DownScan) and side imaging (Garmin SideVü, Humminbird Side Imaging, Lowrance SideScan). On a trolling motor, the sonar its built-in transducer provides. Live sonar is never built in; it needs its own system, listed on each unit's works-with page.

Marine network (Ethernet) ports

Each brand's live sonar (Garmin LiveScope, Lowrance ActiveTarget, Humminbird MEGA Live) and its sonar modules connect over the brand's own Ethernet network. A head unit with no network port cannot run live sonar at all; one with a single port may need a network switch to add a second device.

NMEA 2000

NMEA 2000 is the marine industry's shared data bus. It carries GPS, engine and sensor data between brands, and Lowrance Ghost uses it to talk to the display. It does not carry sonar or live sonar, so having it does not make another brand's sonar work.

Transducer connector

Transducers plug into a unit through a keyed connector named by its pin count (Garmin 4-pin, 8-pin and 12-pin; Lowrance 7-pin and 9-pin; Humminbird 7-pin and 14-pin). A transducer with a different plug fits only through an adapter cable, and an adapter cannot add a sonar type the unit does not decode.

Dimensions (W×H×D)

Width × height × depth in inches, as the brand publishes it. Check the brand's installation drawing before cutting a dash: flush-mount cutouts differ from these outside dimensions.

Size tier

Compact, medium, large or XL by screen size within the unit's own family. The screen size itself is always shown next to it.

Confirmed, inferred, unconfirmed

How a product's data was sourced; see above.