Frederick M. Henschel was elected president of the National Bank of Washington following last week's ouster of Dale L. Jernberg and the dismissal of two of his top officers. Henschel will retain the title of chief administrative officer.

Two directors, John W. Lyon and Irving B. Yoskowitz, also resigned and the board of directors has nominated Washington lobbyist and attorney Thomas H. Boggs Jr. to fill one of those seats.

Henschel joined NBW in 1975 as senior vice president in charge of personnel and administrative services. He was promoted to executive vice president for administration and bank operations and was elected chief administrative officer in 1979.

Henschel takes the helm at a difficult time for Washington's third-biggest bank. A federal grand jury and the Securities and Exchange Commission currently are looking into allegations that some members of the board of directors pushed through large and questionable loans.

Meanwhile, in Baltimore, H. Lee Boatwright III, former president of Suburban Trust Co. of Maryland, was elected president of Central Savings Bank, succeeding C. Edgar Smith Jr., who will become vice chairman of the board.

Boatwright has served as senior vice president in charge of the Baltimore branch of the Federal Reserve Bank of Richmond. Prior to that he was vice president of Mercantile Safe Deposit and Trust Co.