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Mega DI+,
Mega SI+
1,200' 2D
400' DI,
125' SI
AC Live

The HELIX 12 CHIRP MEGA SI+ GPS G3N is one of the newest Humminbird fish finders released in 2019. It also offers a wide array of navigation and networking features, including Radar support and Bluetooth. In terms of sonar, it has the same capabilities as the HELIX 9 CHIRP MSI+ GPS G3N that we’ve already reviewed, and includes the same transducer. However, this is the 12″ version. For reference, this is the Humminbird part number 410920-1.

Key Features and Specifications

    • Display: 12.1″ diagonal, 1280H x 800V pixel resolution, WVGA 16-bit color TFT, with LED backlight
    • Sonar: Dual Spectrum CHIRP, CHIRP MEGA Side Imaging+, MEGA Down Imaging+
    • Transducer: Transom XM 9 HW MSI T
    • Frequency and Coverage:
        • Dual Spectrum CHIRP:

      2D Full mode: 150-220 kHz (adjustable) / 42°
      2D Wide mode: 140-200 kHz / 42°
      2D Narrow Mode: 180-240 kHz / 25°

        • Down Imaging:

      435-535 kHz / 75°
      800-860 kHz / 45°
      1100-1200 kHz / 75°

        • Side Imaging:

      405-505 kHz / 2x 86° / 800 ft (244 m) side-to-side
      780-840 kHz / 2x 86° / 250 ft (76 m) side-to-side
      1050-1175 kHz / 2x 86° / 400 ft (122 m) side-to-side

    • Max. Depth Capability (with the included transducer):
      • Dual Spectrum CHIRP: 1,200 ft (365 m)
      • Down Imaging: 400 ft (122 m)
      • Side Imaging: 125 ft (38 m)
    • Power Output: 1,000 Watts (RMS)
    • Power Input: 10.8-20V DC
    • Power Draw: 1.75 Amp
    • GPS: Internal
    • Cartography: Humminbird Basemap
    • Routes, Waypoints, Tracks: 47; 2,500; 50 (20,000 points each)

Sonar and transducer

As its name suggests, the HELIX 12 CHIRP MEGA SI+ GPS G3N has built-in MEGA Side Imaging+ sonar technology, also offering MEGA Down Imaging+ sonar, and Dual Spectrum CHIRP sonar. Needless to say, the Imaging+ plus sonar technology offers extremely crisp images of structure, bottom, vegetation, and fish, quite an improvement over the last years regular SI and DI.

It supports multiple base frequencies, including 50/83/200/455/800/1200 kHz. Also, since it’s a G3N unit, it has Ethernet and supports Ethernet sonar such as 360 Imaging.

This Humminbird fish finder system includes the MEGA Side Imaging transducer XM 9 HW MSI T. This transducer supports all three types of sonar built-in the unit. It has a metallic transom mount, it integrates a temperature sensor, and has 20′ (6 m) of cable.

For Dual Spectrum CHIRP, this fish finder system offers three main operating modes. These are Full Mode, Narrow Mode, and Wide Mode. Full Mode has a default CHIRP range of 150-220 kHz, but this interval is adjustable. The Narrow Mode and Wide Mode have fixed CHIRP intervals, 180-240 kHz for Narrow, and 140-200 kHz for Wide. The transducer uses conical beams for all these modes, their coverage being 42° for Wide and Full Mode, and 25° for Narrow Mode. Also, the maximum depth capability that the system can reach with the included transducer when using the 2D CHIRP sonar mode is 1,200′ (365 m). However, the system can reach depths up to 3,500′ (1,066 m) if a 50 kHz capable CHIRP transducer is used.

For Down Imaging, the transducer uses oval-shaped, thin beams. The maximum coverage is 75° at 435-535 kHz, and for MEGA DI+ at 1100-1200 kHz. The 800-860 kHz mode offers a coverage of 45°. Also, the maximum depth capability for the unit’s Down Imaging sonar is 400 ft (122 m) at 455 kHz (435-535 kHz), while for MDI+ the maximum depth capability is around 200 ft (61 m).


And finally, for Side Imaging, the transducer also uses oval beams. Their coverage is approx. 86° and they can extend to a side-to-side range of 800′ (244 m). The MEGA Side Imaging+ mode offers a CHIRP range between 1050 – 1175 kHz and a side-to-side coverage of 400′ (122 m), quite a bit more than regular Side Imaging which only offers a side-to-side range of 250′ (76 m). The maximum depth capability of the MSI+ mode is estimated at approx. 125′ (38 m).

Of course, the unit offers a wide array of standard sonar features. The list includes SwitchFire, Real Time Sonar (or A-Scope), Bottom Lock, Selective Fish ID, Circular Flasher, various alarms, Sonar Recording, and more.

Navigation features

First of all, as the unit’s name suggests, Humminbird HELIX 12 CHIRP MSI+ GPS G3N is a GPS unit. It is equipped with a precision internal GPS receiver. It offers WAAS, MSAS, and EGNOS position augmentation possibilities and also has a GPS Speed function. It can save up to 2,500 waypoints in its memory, 47 routes, and 50 tracks with up to 20,000 points per track.

Just like the other Humminbird G3N units released in 2019, the 410920-1 has its own internal chart base – the Humminbird Basemap. This chart base offers detail that is pretty close to the Navionics+ charts. It covers more than 10,000 U.S. lakes, as well as the U.S. East Coast, and West Coast showing a wide array of points of interest such as marinas, hazards, buoys, nav-aids, spot sounding, piers, etc.

Of course, the unit can use various other charts as well. It is compatible with Navionics+, Navionics Platinum+, LakeMaster, LakeMaster Plus, and SmartStrike fishing charts.

Since it’s compatible with Navionics+, the unit offers SonarChart support. However, it has its own similar feature, this being AutoChart Live. This sonar mapping feature uses the GPS data and the 2D sonar data in order to reveal and draw the depth contours of the body of water that you’re scanning. Therefore, you can create your own personalized chart for each lake where you fish, in case the data of the built-in charts is not up to date.

Last but not least, the unit has several other notable navigation capabilities. It has its own internal Radar application and supports Radar modules. It can also provide data from AIS units and supports Minn Kota i-Pilot link, as well as Minn Kota Talon anchors.

Control unit features

The HELIX 12 CHIRP MEGA SI+ GPS G3N features a 12.1″ display, with a pixel resolution of 1280 x 800, and a 16-bit color range. It has LED backlight and provides excellent readability even in direct sunlight or if using polarized sunglasses. It is also IPX 7 waterproof.

Since it’s a HELIX unit, it does not have touchscreen technology. The navigation through its menus and the usage of its internal applications is done via the side keypad. However, the unit has Bluetooth connectivity and you can control it from the distance via an optional RC remote.

The unit has a highly intuitive, easy to use interface with a custom digital readout and the X-Press menu system. It offers multiple split-screen and display customization possibilities.

In terms of networking, the unit is Ethernet and NMEA 2000 capable. Therefore, you can connect it to an already existing boat grid, or to various other instruments such as Radar, AIS units, and more. Also, since it has Bluetooth, you can benefit from software updates or even notifications from your phone through the FishSmart App.

The unit has a dual SD card reader (not microSD). This is quite handy as you can use a map SD card and a data SD card simultaneously, without the need to swap cards.

The classic Gimbal mount is included with this unit. However, the in-dash mounting kit and the unit cover are not included.

The Pros

  • Dual Spectrum CHIRP sonar;
  • MEGA Imaging+ (Side Imaging+ and Down Imaging+);
  • XM 9 HW MSI T transducer included;
  • Metallic transom mount for the transducer;
  • Depth capability up to 1,200 ft with the included transducer;
  • Multiple standard sonar features available, such as RTS, Bottom Lock, Selective Fish ID+, Alarms, SwitchFire etc;
  • Sonar Recording and Screen Snapshot functions;
  • Precision internal GPS;
  • Humminbird Basemap chart platform built-in;
  • AutoChart Live;
  • Supports Navionics+, Navionics Platinum, LakeMaster Plus, and SmartStrike charts;
  • Trackplotting, routes and waypoints functions;
  • 12.1″ display, 1280 x 800 resolution, 16-bit color display, with LED backlight, providing clear images, easy to read even in direct sunlight;
  • IPX7 waterproof;
  • Supports Ethernet and NMEA 2000;
  • Supports AIS and GPS heading sensors;
  • Supports CHIRP Radar and Minn Kota i-Pilot Link;
  • Bluetooth connectivity;
  • Compatible with the FishSmart App and the RC2 Bluetooth remote control;
  • Dual SD card reader;
  • Upgradable internal software;
  • Gimbal mount included;
  • Fairly easy to install.

The Cons

  • In-dash mounting kit is not included;
  • Unit cover is not included;
  • Trolling mount for the transducer is not included.


The Humminbird HELIX 12 CHIRP MEGA SI+ GPS G3N offers MEGA SI+, MEGA DI+ and 2D CHIRP sonar, GPS, and the Humminbird Basemap charts. It includes the XM 9 HW MSI T transom transducer. It also supports NMEA 2000, Ethernet, Radar, 360 Imaging, and more. It also has Bluetooth connectivity. It’s an excellent fish finder and chartplotter for both freshwater and saltwater, perfect for a wide array of boats. It’s not exactly one of the most affordable Humminbird units, but definitely offers excellent value for the price.

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