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Garmin GPSMAP 451, GPSMAP 451s

Product Codes: GAR451 and GAR451S

Garmin GPSMAP 451 and GPSMAP 451s are standalone chartplotters and feature a 4-inch colour display. Both versions of the Garmin GPSMAP 451 marine systems come preloaded with BlueChart g2 marine charts for UK and Ireland and a worldwide basemap. The difference between the GPSMAP 451 and GPSMAP 451s is the s version comes with a sounder for defining depth contours, finding fish and locating objects underwater. You will need to purchase a transducer to enable the sounder to operate.

You can also add further mapping capabilities to the system using BlueChart g3 Vision mapping which provide satellite images and also has an Auto Guidance feature.


Garmin GPSMAP 451/451s has been discontinued.

View latest Chartplotters

Accessories, spares and parts are still available for your GPSMAP 451/451s, as are Garmin GPSMAP 451 g3 marine BlueCharts.

Garmin GPSMAP 451 is a compact chartplotter for use on the water. The GPSMAP 451 features high resolution, bright 4-inch QVGA colour display. The 451 is waterproof to IPX7 standards and the screen has also been enhanced to speed up the map drawing and panning features.

The Garmin GPSMAP 451 comes preloaded with marine charts for the UK and Ireland. There is also a basemap with satellite images. To make navigation quick and simple there is a high-sensitivity GPS receiver. You can also quickly mark and navigate to 3,000 waypoints or 100 routes.

The GPSMAP 451s version includes a sounder. The sounder enables the chartplotter to define the depth of the water, define where fish are and find objects underwater up to 610 metres (2000 feet) below the waters surface. However, for the sounder to function you'll need to separately buy a Garmin Transducer. There are three types of transducers available. The specific one to buy depends on type of vessel/boat/rib and where or how you'd like to mount the transducer. The three are:

‣Transom Mount - for outboard powered boats and fits to the transom of the boat.
‣In-hull mount - for non-outboard powered boats for only single skin fibre glass boats.
‣Through-hull mount - for non-outboard powered boats. Ideal for wooden, steel boats, etc.

To find the perfect transducer to partner your Garmin GPSMAP 451s and your boat please complete our online transducer form. Alternatively, if you know which transducer your require (we do however recommend that you complete our online form to find the perfect transducer) you can view the comprehensive range of transducers available buy from ActiveGPS. Pictured below, transom mounted transducer, thru-hull transducer and in-hull transducer.

The 451s also has an alarm for fish size, shallow and deep water.

Both the GPSMAP 451 and 451S are NMEA 2000-compatible making it simple to connect to sensors, instruments and future marine products providing information such as engine, fuel, wind, VHF, autopilot and other data monitoring.

The GPSMAP 451/451s is preloaded with BlueChart g2 for the entire coastal waters of the UK and Ireland, plus Northen France, Belgium Netherlands and North West Germany which may be all you ever need.

However, the GPSMAP 451 also features an microSD card slot so you can load additional marine charts to the chartplotter. Also available are BlueChart g3 Vision, the g3 Vision version provides extra features including; 3D Mariners Eye for 3D information above the waterline and 3D Fish Eye for 3D information below the waterline. BlueChart g3 Vision maps also feature high-resolution satellite images for help when navigating unfamiliar waters. There is also an Auto Guidance feature that will navigate you along you chosen route avoiding shallow water, buoys and other obstacles.

3-D view of the surrounding area both above and below the waterline.

Garmin g3 Vision are available in a variety of sizes from small areas e.g. Bristol Channel and SW England right up to a large area e.g. Europe Atlantic Coast. Read more information about Garmin BlueChart g3 and g3 Vision charts.

Garmin GPSMAP 451 Features

‣4-inch VGA display
‣Preloaded worldwide basemap
‣Preloaded Garmin BlueChart g2 UK and Ireland
‣NMEA 2000
‣Excellent visibility in bright sunlight
‣Waterproof to IPX7
‣2 microSD card slots allows upgrade to BlueChart g3 cartography and user data
‣1 Year manufacturers guarantee

Sounder functions - GPSMAP 451s model ONLY

‣Sounder power: 500W (RMS), 4,000 W (PTP), with dual frequency transducer
‣Depth: 450m (with dual freq., 500 W transducer)
‣UltraScroll: rapid updating of the sounder image
‣See-Thru technology: shows weak and strong returns simultaneously
‣Auto Gain
‣Split-screen zoom for optimum close-up views of fish and the bottom
‣Alarms for fish size, water depth and voltage

Chart Coverage

Garmin GPSMAP 451 and 451s marine chartplotters are preloaded with Garmin BlueChart g2 UK and Ireland.

Coverage of Garmin BlueChart g2 UK and Ireland chart

Coverage of Garmin BlueChart g2 UK and Ireland chart

The chart (pictured above) features detailed marine cartography coverage of the British Isles in their entirety, including the Thames Estuary, Caledonian Canal, Outer Hebrides, Shetland and Orkney Islands, Isle of Wight, Isle of Man, and the Irish Sea.

Coverage across the English Channel from Douarnenez, France to Emden, Germany, including the Channel Islands, and the Seine River to Rouen, France Detailed coverage includes Antwerp, Belgium, Rotterdam, Netherlands, Amsterdam, Netherlands, and the Ijsselmeer in full. Read more information about Garmin g3 marine Bluecharts.

In future years you can purchase a marine BlueChart g3 update SD card to update the preloaded UK and Ireland charts on the Garmin GPSMAP 451/451s.

What's in the box? (when purchased from

‣Garmin GPSMAP 451/451s
‣Preloaded Garmin BlueChart g2 UK and Ireland
‣Tilt/swivel mount
‣Protective front cover
‣Power/data cable

Garmin GPSMAP 451 Accessories

Looking for Garmin GPSMAP 451 or GPSMAP 451s accessories? Accessories available to purchase include watertight flush mount kit and swivel mounting bracket. If you'd like to add a transducer to your GPSMAP 451s please see this page.

View all Garmin GPSMAP 451/451s accessories

Garmin GPSMAP 451 Maps

Add Garmin BlueChart g3 marine charts to your Garmin GPSMAP 751/751xs, view the different Garmin g3 Bluecharts you can buy from ActiveGPS.

Garmin GPSMAP 451 Technical Specification

‣Technology: GPS
‣Display: 4-inch QVGA display (240 x 320 pixels)
‣Battery: None
‣Waypoints/favourites/locations: 3,000
‣Routes: 100
‣Track Log: 10,000 points, 50 saved tracks
‣Basemap: Worldwide
‣NMEA input/output: NMEA 2000 certified
‣Built-in memory: None (cannot load maps to internal memory)
‣microSD card slot: Yes
‣Garmin radar compatible: No
‣Garmin sonar compatible: GPSMAP 451s only
‣Waterproof: Yes, IPX7
‣Dimensions: Width - 145mm, Height - 127mm, Depth - 69mm
‣Weight: 590g
‣Guarantee: 1-year
Garmin GPSMAP 451 manual

Manual requires Adobe Acrobat Reader
Download a free copy here

This product is a sophisticated electronic device which requires that you read, understand, and act upon the information given in the instruction manual (usually available via the above 'manual' link). You will need internet access and, in accordance with the manufacturers’ recommendations, regularly seek out and accept all firmware or software updates offered by the manufacturer. All GPS devices need to ‘see’ the satellites in the sky. Therefore you will need to know that your vehicle does not have glass that will block or impede the GPS signal.

Updates to this product are via the internet. At this product page we state compatibility with specific versions of current internet connection devices, for example: PC, laptop, MAC, smartphone etc. The Consumer Contract Regulations allow you 14 days, from receipt of purchase, to check compatibility with your internet connection device/s. If you choose to replace or update your PC, MAC etc. neither we nor the manufacturer will be responsible if the new/replacement Operating System (OS) is not compatible with the purchased product.

Why buy from us?

We are official Authorised Internet Retailers for Garmin. We sell genuine Garmin products, accessories and maps. We purchase from assigned Garmin UK distributors. We do not buy on the grey market and we do not sell counterfeit products. You can rest assured that by purchasing from ActiveGPS you will receive the full support of Garmin.

Page updated: 10th March 2020

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