The deal between William T. Young's Overbrook Farm and the Japan Bloodhorse Breeders Association for the sale of Overbrook's first-crop stallion Boston Harbor has been completed. Seven-year-old Boston Harbor left Overbrook near Lexington on Dec. 3. His new stud fee is Y2.8 million (approximately $23,000). The JBBA plans to send him to 90 mares next year.Champion 2-year-old male of 1996 and a $1.9 million-earner, Boston Harbor (Capote--Harbor Springs, by Vice Regent) is represented by stakes winner Boston Twist and the earners of more than $300,000. He ranks 16th on the freshman sires list.