Every marine stereo gets a score from 0 to 100% built from seven factors, which maps onto the 5-point rating shown on the site (a 0% score would be 1.5 stars; a perfect score, 5). Each factor is scored against fixed reference points, not against the other products in the list, so adding a new model never moves another model’s rating. Stereos are grouped by mount, gauge-hole and dash or panel, and use the same scale in both groups.
| Factor | Measures | Weight |
|---|---|---|
| Amplifier power | RMS watts per channel at 4 ohm, never peak or max | 20% |
| Zones | independently controlled audio zones | 15% |
| Pre-amp outputs | RCA output sets for adding amplifiers and subwoofers | 10% |
| Features | NMEA 2000, SiriusXM, phone app, Wi-Fi or AirPlay, weather band, Bluetooth and USB | 25% |
| Water rating | IP rating of the front panel | 10% |
| Display | screen size and color | 10% |
| Warranty | warranty length | 10% |
Where the numbers come from
Power, zones, outputs, features, water rating, display and warranty come from the maker’s spec page, manual or installation guide, or the maker’s own copy on a retail listing. Where a maker’s figures conflict, the headline figure is used and the conflict is noted on the product page. Prices are checked at Amazon and the maker’s own store, and the lowest price at a store the page links to is used.
The factors
Amplifier power is the built-in amplifier’s RMS rating per channel at 4 ohm: 14 W scores zero and 40 W full marks. Peak, “max” and 2-ohm figures are shown in the product notes and never scored, because makers measure them in different ways and they run two to three times the RMS figure.
Zones is the number of audio zones the stereo controls at separate volumes: one zone scores zero and four zones full marks. A stereo whose maker describes no zone control counts as one zone.
Pre-amp outputs is the number of RCA output sets for external amplifiers and subwoofers, counting each zone’s line out, a rear pair and each subwoofer out as one: one set scores zero and eight sets full marks.
Features is 20% for built-in NMEA 2000 (control from a chartplotter), 15% each for SiriusXM-ready, a maker’s phone app, Wi-Fi or AirPlay 2 streaming and a NOAA weather band, and 10% each for Bluetooth and USB music playback. A feature that needs a separately sold module, such as a CAN-bus adapter, doesn’t count.
Water rating is the IP rating of the front panel, by its water digit: IPX5 scores 40%, IPX6 70%, and IPX7 or better full marks. A rating of IPX4 or lower scores zero.
Display is 60% for screen size, from 2 in (zero) to 4.3 in (full), and 40% for a color screen.
Warranty is the maker’s warranty: 1 year scores zero and 3 years full marks.
What isn’t scored
Price, pre-out voltage, DAB+ (sold in Europe and Australia), CD playback, camera inputs, a touchscreen, the number of amplified channels and release date are listed but not scored. Dealer warranties that apply only to some sellers are not counted as the maker’s warranty.
Missing data
If a figure isn’t published, that factor gets the neutral middle score (50) and the product page marks it as estimated. A display with a known type but no published size scores neutral on size. Features score neutral only when none of them is published; a feature the maker doesn’t mention otherwise counts as absent. The exception is warranty: a maker that doesn’t publish one gets no warranty counted, so that factor scores zero, the same as a one-year warranty, and is marked estimated.
Ties and discontinued models
Products are ranked by score within each group. Discontinued models stay listed but rank below every current model and can be hidden with the “Hide discontinued” filter.