Editor’s Note – This post is provided by Capt Pancho of Nassau, Bahamas
The Garmin 640 is a semi-portable GPS unit with a 5.2″ touch screen pre-loaded with both US street maps and US coastal charts. The unit comes with 2 mounting configurations, car and marine, and can be added to your NMEA network as well as receive weather, traffic and music via a separate XM satellite antenna.
It’s size and portability make it useful for a traveling boat captain or the weekend boater. I feel that most of the chartplotters available provide similar functions, so I’ll focus on the differences and how they affect the boater.
I use my Garmin 640 on board a 65′ charter sailboat, SCUBA diving and fishing the Bahamas for a week at a time, in all weather and all seasons. At the helm, the 640 sits in the marine bracket and is hardwired into the boat, with the XM antenna attached. The boat I run has also has a large screen Garmin chartplotter at the helm, and my first mate carries a Garmin handheld GPS as well.
The Garmin 640 is very handy and helpful for storing my personal waypoints and accessing the weather forecasts provided via XM. The data is presented differently than on previous marine models, and the experienced user will likely find a learning curve before getting comfortable finding the pages or data you are looking for. I’m not sure if the new layout is an improvement, but when my crew attempts to use the 640, most are quickly frustrated as we are all accustomed to using the older Garmin 2006, 60, 76 and 486, which are all very similar to each other. We generally agree that the new menu trees are too complex, require too many keystrokes, are not as intuitive as older units, and work differently depending on which page you are viewing.
For example, the “back” button will take you back any where from 1 to 4 pages in a single keystroke. As for route planning, we all revert to the familiarity of the Gamin 2006. For weather and tides, the Garmin 640 is the fastest and easiest to use.
Garmin Tech support will tell you that they consider this 2 separate units in one housing. What this means to you is that the Street Maps and automotive functions can be accessed and managed on your computer via the USB cable included in the box. You can change the vehicle icon, download new vehicles and update the software using USB. However, the marine functions CANNOT be accessed via USB. This confused me at first. You’ll need to insert an SD card into the Garmin 640 to format the card, then put the SD card into the card slot in your computer. The Garmin software will detect your GPS unit, not the SD card! Don’t fret, the computer thinks the SD card is the GPS unit! Now, you can manage your waypoints and routes from your computer, which is much easier than on the touch screen. If you use the touch screen to make waypoints, you’ll notice that the “key board” is not a QWERTY key board; instead, all of the letters run alphabetically from the top left. This frustrates all of my crew, from college grads to the ones who never finished high school.
The Hardware: The touch-screen works well, even when wet. You must press a little harder than an iPhone and drag your finger slower. It is easy to read in bright light or at night, however, you can’t dim the unit enough to preserve your night vision. The light level goes from very bright, to medium bright. There is no internal speaker, so I ran an audio cable to the stereo system. When we anchor out on the Great Bahama Bank, I use the GPS’s anchor alarm feature, in order to get a full night’s sleep. The battery is not strong enough to power the unit for more than 5 or 6 hours and since there is no internal speaker, I use the automotive mount in the cabin with an external speaker built into the 12-volt cigarette-style plug. Once again, the unit can’t be dimmed down very far, so I cover the screen. The 640 will switch to automotive mode, but you can switch back to Marine Mode….however, sometimes the unit will mysteriously change back to Automotive mode during the night! This is scary, since I cannot put much faith in the anchor alarm.
The antenna is very strong, however, and I don’t need a separate GPS antenna down in the cabin, unlike Garmin’s 76 or 60csx or the 486! (Plus the swivel mount antenna on the 486 seems to be a continual problem for my mate.) Neither mounting configurations will work or adapt to previous Garmin mounts, like the old bean bag mount which was uglier but much more functional. Garmin’s choice to use SD cards in stead of their old chip sets is a vast improvement.
XM weather and music: I have good to excellent XM satellite coverage as far as the Exuma Cays and Eleuthera, in the Bahamas. The XM antenna needs a few extra seconds, up to a minute, to acquire the satellites, but then provides music and land based weather quickly. For some reason, the marine forecasts are slower to load and are often not available. Since the XM signal is strong, I’m assuming this is due to the forecasts themselves not being updated. To get the marine coastal forecast for your area, you often must “hunt around” on the touch screen to find an available forecast. Strangely enough, hurricane forecasts are easier to find on the “precipitation” page, not the “forecast” page. The XM antenna has been living in the sun and salt for about a year now and has held up well, but the cheap metal bracket provided with it rusted very quickly.
Warranty and Tech Support: When I first subscribed to XM’s Master Mariner package, the unit would not initialize until the 5th attempt and several calls to XM and Garmin. Also, Garmin’s Tech support was unable to help with my confusion regarding using the SD card and not the USB cable (as in my previous Garmin GPS units). Ultimately, I contacted one of Garmin’s outside sales reps, who helped me transfer my waypoints and explained how the unit works.
The Garmin 640 is rated to be waterproof to 3 feet but when my unit fell into a foot of saltwater in the inflatable tender it flooded. I opened and washed it carefully with electronic cleaner then let it dry for 2 days and it worked flawlessly afterwards. I sent it to Garmin after their Tech Support department said they would make sure that it was OK or they would replace it.
Comments for Garmin 640
Average Rating 
The 640 is not a good chartplotter- nextThe “auto routing” function does not work with the standard map, it will only work with G2 maps. It doesn’t work with my Euro map of the French-Spanish coast.In my opinion, auto routing is a dangerous and stupid way of having the instrument take over the planning of a sea or coastal route.The “numbers” and “compass” screen show fields that cannot show the VMG. Most info is predefined and and cannot be altered by the user. The menu says VMG is available on the “numbers” screen, but it really displays “wind VMG” :whatever that parameter is! Useless for boats without wind meters.The compass screen shows nice colors that would indicate obstructions. The compass navigation parameters can’t be chosen as in the older Garmin’s. Most people look at the map and see for themselves if there are obstructions. This type of route display is a failed strategy of trying to have auto route at sea like you had for a car.By the way If you would need a Garmin for your car, buy a lightweight Nuvi, they have more options than the ultra-basic functionality in the land-car navigation that is in the 640.Because of the clumsiness and weight of the 640 you would never switch GPS from boat to car very often, unlike in in emergency situations. On a boat is weight not a problem but transferring it back and forth from car to boat is. A heavy unit in a car is a danger in accidents and could damage something when braking or executing a sharp turn.I am really angry with Garmin over this instrument. It is a frustrating to go backwards in functionality of a sea instrument. I use my small screen Garmin Oregon more to navigate on the boat than the less than stellar 640.I did send Garmin a message over the lack of options a year ago. The only answer I got was that I have to live with it and that there is a very limited VMG capability in the unit. The lack of good VMG info onscreen which cannot be adapted to your taste is terrible. Only a motor boater could do without VMG, but I think even motor boaters could use VMG and an easier route making scheme like a “new route” menu item feature.
The consumer zombies that would need an “auto routing” on the ocean are not fit to be on the sea in the first place. This instrument doesn’t give you control over navigation, it tries to take control over you. I am worried for the whole series of Garmin navigators. The Garmin user interface philosophy has clearly changed. Are these as bad as this 640 in functionality? This will be my last Garmin.
I almost agreeI think this review was a little too forgiving – I find the screen very difficult to view in bright sunlight and that difficulty to be compounded if viewed at an angle and forget it if you are wearing polarized sun glasses. I understand the comments made regarding the difference in operation from other Garmin products but I guess I am more forgiving in that aspect of this unit. I bought my unit as a backup on my sailboat because my radar/plotter is a combined unit and my fear was if one failed they both failed. The road map capability is a plus when you are in a port, in the USA, and rent a car to go sightseeing.
Great Review of the Dual Purpose Garmin 640Pancho, thanks for a great review of this Garmin dual-purpose chartplotter.