Small boat sailors often ask about handheld GPS units.
Portability is important to me as I use mine for road/marine/air travel frequently here and overseas trips.
Ive found the Garmin 76 Map series to be an excellent choice. I have an older GPSMap76S model with grey screen that is still available for around $400. The newer models have color, more memory and you can still download the BlueMap series charts for Marine, city/highway or aviation use. Go to this link for more on the various models in the Garmin 76 Series.
[http://www.garmin.com/products/gpsmap76s/]
A big plus is the BlueMap software that allows you to plan and do post trip reviews. Very slick! Garmin also makes other small units that can be adapted for marine/land/air purposes but they are larger and not as easy to carry in your pocket. I really, really, like the G276 but its a little bulky for my taste and youll spend about $700. The G376 is even more slick with all the features of the G276 but with XM radio and weather. Youll spend over $1000 for that package plus a monthly subscription. For more on the G76 in action go to this link:
[ http://kobernus.com/hunter260/gps/gps1.html ]
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The stock GPS mount from Garmin is expensive and flimsy. RAM makes a much better mount for about the same price. Search the internet for RAM-B-138-GA6U mount and the RAP-326 Ezy-mount quick release adapter.