I've got a 73dv. When I input some GPS coordinates then look at them on the map, it shows to be on land. It's in the general area, but shows in the middle of a house. I got the coordinates from Google Earth. So which one is right? And how do I fix it?

Check and see what format your charts are set up for, because there are like 4 different formats.

http://www.earthpoint.us/Convert.aspx

This is the easiest converter I've found.