Since you are using v3, you can simply prevent the infoWindow from shifting the map with the disableAutoPan
option, as in the following example (API Reference):
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8"/>
<title>Google Maps disableAutoPan Demo</title>
<script src="http://maps.google.com/maps/api/js?sensor=false"
type="text/javascript"></script>
</head>
<body>
<div id="map" style="width: 200px; height: 200px"></div>
<script type="text/javascript">
var myLatlng = new google.maps.LatLng(37.44, -122.14);
var myOptions = {
zoom: 4,
center: myLatlng,
mapTypeId: google.maps.MapTypeId.ROADMAP
}
var map = new google.maps.Map(document.getElementById("map"), myOptions);
var infowindow = new google.maps.InfoWindow({
content: 'Test',
disableAutoPan: true
});
var marker = new google.maps.Marker({
position: myLatlng,
map: map,
title: 'Test Marker'
});
google.maps.event.addListener(marker, 'click', function() {
infowindow.open(map, marker);
});
</script>
</body>
</html>
Screenshot: