Sheriff's officials in St. Louis County christened a new high-tech rescue and patrol boat on Tuesday.  A federal stimulus grant paid for the 28-and-a-half-foot vessel built by Fraser Shipyard in Superior.  It will be used for water patrols and search-and-rescue operations in the Duluth Harbor and on the Saint Louis River and western Lake Superior.  The boat was custom built and designed with the latest navigation technologies and is equipped to handle sonar and underwater robotic tools.  The Saint Louis County Sheriff's Office and Rescue Squad is expected to use the boat for more than 30 years.