I have the Magellan eXplorist 200. I think they will have the same way of doing this, so here goes. You do not need to have a position fix to mark them. Go to the map screen. Move the arrow buttons in any direction until it says "Cursor" at the bottom. Push "Mark". It doesn't matter where the cursor is. When it gives you the screen to edit the settings of it, set the name, the description (if you want it) and you can change the lat. and long. there also. Highlight the area where the lat. and long. are listed, then press enter. Now you can edit the lat. and long. Edit it, then hit save. Then press Go to. Find that POI on your list, then hit enter. You now have the straight path to the cache (or whatever it was you marked:)). Good luck!