"Has anyone adapted a car navigation unit to display marine
I read that Amazons latest Kindle,for about $140,can display charts."
Not really. Dedicated car navs almost invariably can't be loaded with anything except the maps sold by the maker--for roads. You'll find that Garmin
and others who make a very few models that can take marine and other maps, advertise those units as "special" not just car navs. And if all you need is a tiny snippet of chart...sure, that'll work. With limited chart support.
As to the Kindle? Fuggedaboudit. E-book readers are designed with daylight-readable low-power inexpensive displays, and so far, that means they all (ALL) wink, blink, nod, and pause before screen
refreshes. If you can load charts on it, don't expect them to scroll. Smartphone displays are meant to handle live video, as are tablet computers
. E-readers are meant to show one static page, take a break, show the next.
Give it a few years, things will keep improving. For now, it's a matter of choosing your poison:
All of which may be fine, if you want a backup, or something dingy-pocket-portable.