James E. Turner will retire as president and COO of General Dynamics on January 15 - a position he has held since June 1997. Turner, who also led the company's Marine Systems Group since October 1995, joined the company in 1988 as vice president and general manager of Electric Boat - the company's nuclear submarine division. The company expects to elect a leader of the Marine Systems Group in January 2000; it does not plan to name a president.