The Google Maps documentation indicates that adding a title
property to a Marker object will result in its value appearing as a tooltip when the user hovers ove
The linked example uses the experimental version.
You should always use the release-version( https://maps.googleapis.com/maps/api/js?v=3) when you use the API in production, the tooltip will work with the release-version: http://jsfiddle.net/doktormolle/6kUaU/ .
Possibly related issue in the Google Maps API issue tracker: