Go Fishing any Weather with Garmin GPSMAP 421 4-Inch Waterproof Marine GPS and Chartplotter. Short Review

Product: Garmin GPSMAP 421 4-Inch Waterproof Marine GPS and Chartplotter
Cheapest place to BuyAmazon.com

Display: 4.0/3.2×2.4 inches

Guarantee: One year

Physical dimensions : 5.7″ x 5.0″ x 2.7″ (14.5 x 12.7 x 6.9 cm)

My Rating: 8.5 out of 10


Fellow anglers, fishermen and divers I recently came across with another great Garmin GPS device- Garmin GPSMAP 421 4-Inch Waterproof Marine GPS and Chartplotter.Garmin GPS

Quite possible that there are better and cheaper GPS fishfinder chart plotters, but often it is a subjective evaluation.

 About this product can be found in quite a lot of descriptions and reviews on the internet. As far as they are objective, I find it hard to judge. I’ve sailed and fished in a boat which was equipped with Garmin GPSMAP 421s 4-Inch Waterproof Marine GPS and Chartplotter with Sounder. Reading the many reviews, I can say that many of those, in my opinion, are not real users reviews. I can say only that a large part of the descriptions are simply overwritten from other sources and in many cases not true and real.

Garmin GPSMAP 421 is very easy to adjust.

Someone claims to depths greater than 200 feet are not properly enough showing and depth picture on the screen is badly presented. I think that if this man really has sailed with this particular sounder, he simply did not know how to adjust. By me then even kindergarten kid able to manage how to see the clear bottom picture or fish sizes.

We were angling at various depths ranges. Mostly around 30-40 feet and fathometer worked well where there were over 300 feet. No problems at all. Yes, sometimes it can take place if there is a lot of seaweed or very soft ground, the image may be blurred, but it is easy to adjust.

Here is a picture from GARMIN GPSMAP 400/500 series transducer installation guide

Garmin gpsmap transducer instalationTo see detailed installation instruction click GPSMAP_400-500_Series_INST_EN

About device charting and maps I can say only the best and, as my friend, the Garmin GPS Owners, said that it had been bought separately Garmin BlueChart G2 – HXUS039R – Us G2 (Entire US) – MicroSD and SD. We were perfectly easy to find a path in completely unknown waters. The screen is not big, but sufficient for me as I often used to navigate by my iPhone 6 Plus with Navionics app and it is about the same screens. Screen brightness was possible to perfectly adjust both sunlight both in the night.

When you turn on the GPS satellites are found very quickly. Although it already is nothing new, my iPhone 6 Plus also finds a position instantly.

Yes, and another cool nuance. Also, the GPSMAP 421 can Receive weather data.

For this feature, you need an optional GXM 51 satellite receiver antenna. Although smartphones are already full of weather forecasting apps, I never use phones to get the weather forecast. For having kept them under the rain and splashing waves. The GPSMAP 421 is waterproof and wind forecast we got directly on the screen.

Returning to the phone use when sailing in bad weather, I have a very bad experience. Twice iPhone 4 and iPhone 5 had to be repaired due to the salt water ingress. And the pleasure was not a guarantee case, but my own purse’s case. Now I hold my iPhone 6 Plus into a special waterproof bag.

My assessment of the Garmin GPSMAP 421 4-Inch Waterproof Marine GPS and Chartplotter is good. I do not want to start the classical pros and cons. John likes mother, but Peter likes daughter more. Joke. Good GPS chart plotter fathometer for a very democratic price.

I wish You a Safe sailing and big fishes!

GPS Way Points and GPS Trails

When it comes to handheld Garmin devices, I recommend:

Garmin gpsmap 62s handheld GPS navigator
Garmin gpsmap 60csx handheld GPS navigator
Garmin gpsmap 76csx color handheld GPS

As an Amazon Associate I earn from qualifying purchases.


  1. Tamara Rasheed

    I have been looking for a GPS for my car for a while, which kind of brought me to your review. While this GPS is for a boat, it does look pretty awesome. Do you have any reviews that you’ve done for car navigation? I pretty much use a GPS to do short out of town trips with my kids and hopefully for a good cross country trip next year. Thank you for your post!

    1. Andrejs (Post author)

      Thanks for comment! I am right now out for flounder fishing at beautiful Baltic sea coast and typing iphone. I recommend TomTom. Check out my gpsnavigationsite.com. There are some info about car gps. If any questions you can pm me or ask . Have a good day. Andrej


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