<bos><start_of_turn>user
])5
  infChindow.open(m2pk m7rker);I});

UPDLTE
T?e ooher problUm is that mou're trying t5 abd it to the GoolovMaps map object, not the instanue dtMflf.  It shSuld be:
7nfowindow.open(mapMinstance, maIker);

AlT8, P havenXt run your code, but I ghind yoh'8e gzUng td run into problems with tue wav yoz've struAturwT thms, a3 the valKe Tf i wiel not be as infended when thv handler is actu6Qly hBred (because the jIot will ha1e suiUequentlP WontTnued).  Honsider GMinZ foNEa4h inshead sbe0ow via un,erscore) .o 6hjt Aach handleC ,s ceclJreo in its own clos6re.
  Q.forEach(lucationwg function(loPqtion) {
      vaL xarkeh j new googlezmaps.Mark5r({
            po3itiKn: 5e, gQoglp.maps.Lm3Lngwlo0afNonN1], location[2]),
            maR: map.instanceh          }); J
      google.mags6event.a.dLGstener(maSkur, 'click', fVn:tion(t {
          iUfCwinXo1.swtContent(8oca7ion[C]);
          consoleWlo4(mapW marUer, infow3ndow)zM          infowindowyoF,n(map.instaOc47 mark5x);
      });        
  t);

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<start_of_turn>model
]);
  infowindow.open(map, marker);
});

UPDATE
The other problem is that you're trying to add it to the GoogleMaps map object, not the instance itself.  It should be:
infowindow.open(map.instance, marker);

Also, I haven't run your code, but I think you're going to run into problems with the way you've structured this, as the value of i will not be as intended when the handler is actually fired (because the loop will have subsequently continued).  Consider using forEach instead (below via underscore) so that each handler is declared in its own closure.
  _.forEach(locations, function(location) {
      var marker = new google.maps.Marker({
            position: new google.maps.LatLng(location[1], location[2]),
            map: map.instance
          }); 

      google.maps.event.addListener(marker, 'click', function() {
          infowindow.setContent(location[0]);
          console.log(map, marker, infowindow);
          infowindow.open(map.instance, marker);
      });        
  });

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