arrMarkers = [];
var map;
  
function addMarker(coords1, coords2, description) {
     var marker = new GMarker(new GLatLng(coords1, coords2));
               GEvent.addListener(marker, "click", function() {
                     marker.openInfoWindowHtml(description);
               });
      clusterer.AddMarker(marker, description);
}

function showMarkers() {
   var mgr = new GMarkerManager(map);
   
   mgr.addMarkers(arrMarkers, 7);
   mgr.refresh();
}