Waite Hoyt, the top pitcher on the powerful New York Yankee teams of the 1920's, died yesterday in Cincinnati. He was 84 years old

Mr. Hoyt had been hospitalized in Jewish Hospital in Cincinnati for several weeks after suffering a heart attack.

In his 21-year major league career, he recorded 237 victories and 182 losses, and his earned-run average was 3.59. In 1969, he was elected by the Veterans Committee to baseball's Hall of Fame.

One of Youngest to Sign

Mr. Hoyt was one of the youngest players ever to sign a major league baseball contract. Born in Brooklyn on Sept. 9, 1899, he was a 15-year-old sophomore at Erasmus Hall High School when he signed with the New York Giants, and he finished the 1915 season pitching batting practice for the team.

Although touted as the ''Schoolboy Wonder,'' the young right-hander spent three years in the minor leagues before the Giants gave up their rights to him and he went to the Boston Red Sox in 1919. The following year, after an injury-ridden season in which he won 6 games and lost 6, he was traded to the New York Yankees, for whom he became an instant success. In 1921, when the Yankees won their first American League pennant, the 21- year-old Hoyt posted a record of 19-13. In the World Series against the Giants, the first New York ''subway series,'' he won two games before losing the final one, 1-0, on an error. He thus tied a record set by Christy Mathewson in 1905 by pitching 27 World Series innings without allowing an earned run.

Mainstay for the Yankees

In ensuing years Hoyt continued as a mainstay for the Yankees, and in 1927, with the famed ''Murderers' Row'' team of Babe Ruth and Lou Gehrig, he had one of his best years. He led the American League in victories, with 22, and earned run average, 2.63. The Yankees went on to win the World Series in four straight games from the Pittsburgh Pirates, with Hoyt winning the first game.

He followed with an equally strong season in 1928, winning 24 games and losing 7 and going on to beat the St. Louis Cardinals twice as the Yankees again swept the World Series in four straight.

In all, Hoyt pitched in seven World Series, posting a 6-4 record. Traded to the Tigers

During the 1930 season Hoyt was traded to the Detroit Tigers, and the next three years he was dealt in turn to the Philadelphia Athletics, the Brooklyn Dodgers and the Giants, finally ending his wandering with the Pirates, for whom he pitched for four years.

As his career wound down, Hoyt returned to the Dodgers in 1937 and retired from the major leagues in the middle of the following season. But baseball was not yet out of his blood; he pitched the rest of the 1938 season for the semipro Bushwicks, also in his native Brooklyn.

During his playing days Hoyt appeared frequently as a guest on radio shows, and, a skilled storyteller, he became one of the first players to switch to commentary after retirement from playing. In 1942, he began broadcasting Cincinnati Reds games and when television came along after World War II he broadcast simultaneously over radio and television. Pallbearer for Ruth

In 1948, he was an honorary pall bearer at Ruth's funeral, held on a sweltering day at St. Patrick's Cathedral in New York.

He remained as the voice of the Reds until he retired from broadcasting in 1965.

Hoyt is survived by his wife, Betty, of Cincinnati; his sons, Christopher, of Fairfield, Conn., and Harry, of Fort Lauderdale, Fla., and a daughter, Doris Niccum, of Parker, Pa.

Funeral services will be held on Wednesday at Christ Church in Cincinnati.