A Boston Duck Tours amphibious vehicle churning through the Charles River was evacuated Friday after the engine began smoking, State Police said. Employees aboard the duck boat noticed the smoke at about 12:15 p.m. and suspected that a radiator hose might have burst, said Bob Schwartz, director of marketing and sales for Boston Duck Tours. Schwartz said employees did not see any flames. No injuries were reported, said State Police spokesman David Procopio. A State Police boat was on the water near the Museum of Science when it saw the duck boat in distress, Procopio said. Passengers were transferred to the State Police boat.