It has to be a brand/type the unit supports. Navionics,C-map, bluenav, etc.Start here:http://www8.garmin.com/manuals/GPSMAP185Sounder_OwnersManual.pdf
at lease he buys things , unlike you
so you just come over here when you need something bngh bngh bngh bngh bngh bngh bngh bngh bngh bngh bngh bngh bngh
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