Question

Can I change marker size on hover? I need increase marker size on hover (2-3 px) and decrease to default size on mouse out.

Answer 1

If you use a custom-icon, you can easyly change the image on mouse-over :

[...]

var marker_image_medium = new google.maps.MarkerImage('medium.png');
var marker_image_big = new google.maps.MarkerImage('big.png');

var marker = new google.maps.Marker({
    position: myLatlng, 
    map: map,
    icon: marker_image_medium,
    title: "Exemple"
});

google.maps.event.addListener(marker, 'mouseover', function() {
    marker.setIcon(marker_image_big);
});
google.maps.event.addListener(marker, 'mouseout', function() {
    marker.setIcon(marker_image_medium);
});

This is a partial example, you have to init the map, declare myLatlng, etc.

Edit : oups, small error on setIcon(), corrected.