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1,200' 2D
350' DI,
125' MDI

AC Live

The HELIX 8 CHIRP MEGA DI GPS G3N is one of the new 8-inch Humminbird fish finders released at the beginning of 2019. It offers the same sonar and navigation features as the HELIX 7 CHIRP MEGA DI GPS G3N that we’ve already reviewed here, but does have a richer pixel resolution, and a dual microSD card reader. For reference, this is the Humminbird part number 410820-1 which includes the MEGA Down Imaging transducer.

Technical Details and Specifications

  • Display: 8″ diagonal, 1024H x 600V pixel resolution, WVGA 16-bit color TFT, with LED backlight
  • Sonar: Dual Spectrum CHIRP, CHIRP Mega Down Imaging
  • Transducer: Transom XNT 9 HW MDI 75 T
  • Frequency and Coverage:
    • 2D Narrow Mode: 180-240 kHz / 25°
    • 2D Wide mode: 140-200 kHz / 42°
    • 2D Full mode: 150-220 kHz (adjustable) / 42°
    • Down Imaging: 440-500 kHz / 75°
    • Mega Down Imaging: 1075-1150 kHz / 75°
  • Depth Capability (with the included transducer):
    • Dual Spectrum CHIRP: 1,200 ft (365 m)
    • Down Imaging: 350 ft (106 m)
    • Mega Down Imaging: 125 ft (38 m)
  • Power Output: 1,000 Watts (RMS)
  • Power Input: 10.8-20V DC
  • Power Draw: 1 Amp
  • GPS: Internal
  • Cartography: Humminbird Basemap
  • Routes, Waypoints, Tracks: 45; 2,750; 50 (20,000 points each)

Sonar and transducer

To begin with, the Humminbird HELIX 8 CHIRP MEGA DI GPS G3N supports multiple base frequencies, including 50/83/200/455/800 kHz, and 1.2 MHz. It offers two main types of sonar; these are Dual Spectrum CHIPR and Down Imaging which also includes the MEGA DI mode. On top of that, since it’s an Ethernet unit, it can support 360 Imaging sonar if paired with a 360 Imaging transducer.

For Dual Spectrum CHIRP, the unit makes available three distinct sonar modes. These are Full Mode (150-220 kHz), Narrow Mode (180-240 kHz), and Wide Mode (140-200 kHz). The CHIRP intervals for Narrow and Wide mode are fixed; the Full Mode interval is adjustable. The 150-220 kHz is the default range, but you can adjust it between 140-240 kHz.

For Down Imaging, you can use the regular mode at 455 kHz (440-500 kHz) for a better depth capability, or the MEGA DI mode at (1075-1150 kHz) for maximum imaging sharpness.

The unit comes with the new XNT 9 HW MDI 75 T transducer which integrates a temperature sensor, has a transom mount, and 20 ft (6 m) of cable. This transducer supports both Dual Spectrum CHIRP and MEGA DI. It is basically a High CHIRP transducer as it does not support 50 kHz or 83 kHz CHIRP ranges.

For the unit’s Dual Spectrum CHIRP sonar, the transducer uses conical beams. Their coverage is 42° for Full Mode and Wide Mode, and 25° for Narrow Mode. Its maximum depth capability is 1,200 ft (365 m) when using Wide Mode. However, if the unit is paired wit ha 50 kHz CHIRP transducer, it should be able to scan depths up to 3,500 ft (1,066 m).

For Down Imaging, the transducer uses oval-shaped beams, approx. 1°-2° fore-to-aft, but wider side-to-side. Their coverage is approx. 75° and the depth capability is 350 ft (106 m) for regular Down Imaging and 125 ft (38 m) for MEGA Down Imaging.

The unit offers a wide array of highly useful sonar features and functions. Among them, we can count SwitchFire, Selective Fish ID, Bottom Lock, Real Time Sonar, Depth Alarm, Fish Alarm, Screen Snap Shot, Split Zoom, and more. The unit also has a Temperature Graph function which can be very helpful if you’re looking for surface currents of different temperatures. It also has Sonar Recording, but in order to use this feature, you will need a data microSD card inserted into the unit to serve as support for the recording.

Navigation features

The HELIX 8 CHIRP MEGA DI GPS G3N comes with the Humminbird Basemap charts. It is also compatible with Navionics Platinum+, Navionics Plus, LakeMaster, LakeMaster Plus, and SmartStrike charts. But nonetheless, the built-in Humminbird Basemap offers charts for more than 10,000 U.S. lakes. They are based on NOAA charts and offer precise data for the U.S. coast as well, showing hazards, buoys, marinas, hotels, camping sites, spot soundings, daymakers and more.

In case the Humminbird Basemap charts don’t offer satisfying detail for your lake, the unit also has the AutoChart Live feature. This is a depth contour recording application which uses the 2D sonar data and the GPS data in order to reveal and draw the depth contours of the lake you’re scanning on the map.

AC Live can record and save up to 8 hours of mapping in the unit’s internal memory, but you can expand the recording capabilities with a Zero Lines microSD card. It also has bottom hardness, vegetation data, and depth range shading so you can easily view the safest path for navigation.

This HELIX 8 unit is equipped with a precision internal GPS receiver and also supports external GPS heading sensors. It can provide position enhancements by MSAS, WAAS, or EGNOS. It has a GPS speed function so the unit can calculate the speed of your boat. It also offers the possibility to create and save up to 2,750 waypoints, 45 routes and record up to 50 tracks, with up to 20,000 plot points per track.

Last but not least, since this is a G3N unit (not G3), it supports Radar, Minn Kota i-Pilot Link, Minn Kota Talon Shallow Water Anchor, and information from AIS units.

Control unit features

The HELIX 8 CHIRP MEGA DI GPS G3N features an 8-inch display with a richer, 1024H x 600V pixel matrix than the 7-inch unit. Needless to say, it’s a full-color display with integrated adjustable LED backlight. It is also IPX7 waterproof which means it’s built to support incidental water exposure and even immersions in freshwater.

The included mount is the classic Gimbal type. The in-dash mounting kit and the unit cover are not included.

The unit does not have touchscreen technology, though. The navigation through its menus and functions is done exclusively from the keypad on the right. Its interface is highly intuitive and very easy to use.

The unit has Bluetooth technology. This allows you to sync it with your smartphone via the FishSmart App, in order to get notifications and use other features. The Bluetooth connection also gives you the possibility to easily download software updates when they are available. It’s also compatible with the RC2 Bluetooth remote control which allows you to control most of the fish finding and navigation features without touching the unit.

As opposed to the G3 units, the HELIX 8 CHIRP MDI GPS G3N offers Ethernet and NMEA 2000 capabilities. Therefore, you can interlink it with different other Humminbird units, or other navigation instruments, such as AIS units, Radar units, i-Pilot Link etc.

The unit has a dual microSD card reader. Therefore, you can use up to two microSD cards simultaneously, one for charts, one for data back-up for example, or two separate chart charts so you can swap whenever you want.

The Pros

  • Dual Spectrum CHIRP sonar;
  • CHIRP Mega Down Imaging and regular CHIRP Down Imaging sonar;
  • XNT 9 HW MDI 75 T transducer included;
  • 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;
  • Route and waypoint creation functions;
  • Trackplotting function;
  • 8″ display, 1024 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 microSD card reader;
  • Upgradeable internal software;
  • Gimbal mount included;
  • Fairly easy to install.

The Cons

  • Bluetooth remote control not included;
  • In-dash mounting kit not included;
  • Unit cover not included.


The Humminbird HELIX 8 CHIRP MDI GPS G3N is a fish finder and chartplotter combo, offering Dual Spectrum CHIRP, Mega Down Imaging, GPS, the Humminbird Basemap charts, and AutoChart Live. It includes the XNT 9 HW MDI 75 T transducer and also supports Ethernet, NMEA 2000 and various add-ons via such networks, including CHIRP Radar and i-Pilot Link. The unit also has Bluetooth connectivity. In all, it’s a pretty versatile unit, great for a wide range of boats, for both in-land and off-shore fishing.

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