you have to set the setSelect
option while creating the jcrop
$('#previewImg').Jcrop({
onChange: showCoords,
onSelect: showCoords,
setSelect: [0, 160, 160, 0],// you have set proper x and y coordinates here
minSize:[300,100],
maxSize:[900,900],
aspectRatio: 3/1
});
Here is the demo for setSelect option http://deepliquid.com/projects/Jcrop/demos.php?demo=advanced