James A. Dalrymple, the 50-year-old director of the University of Florida's Stephen C. O'Connell athletic arena, has been selected to replace Robert H. Sigholtz as the new general manager of Robert F. Kennedy Stadium and the D.C. Armory complex.

Sigholtz, manager of the complex for the past 11 years, was told earlier this year that his contract would not be extended when it expired at the end of the year. But on Wednesday, he said, Mayor Marion Barry told him his duties at the complex were to end yesterday.

The change in general managers was approved by the three-member D.C. Armory Board -- Barry, who heads the panel, restaurateur Stuart J. Long and Maj. Gen. Calvin G. Franklin, commanding general of the D.C. National Guard and head of the board's personnel committee.

Franklin said yesterday that Dalrymple was selected by an executive search committee that "cost us a lot of money." He said Dalrymple will begin work on Tuesday, and declined to give further details about the new director.

Dalrymple, reached at his home in Turkey Creek in Alacuha County, Fla., said yesterday that he has not signed a contract but will arrive here today and expects to sign a two-year contract with an annual base salary of $57,000.

Dalrymple said he has been director of the University of Florida's O'Connell Center, a covered arena that seats 12,500 persons, since 1980.

For 21 years, he said, he was director of a number of public facilities in Winston-Salem, N.C., including Bowman Gray Stadium and the M.C. Benton Convention Center. Dalrymple said revenues for the Winston-Salem facilities that he managed ranged between $3 million and $4 million a year.

A former football player for Wake Forest University, Dalrymple said he was asked to try out for the Washington Redskins in 1959 but never came because he decided that he "needed to get a job and support his family."

Sigholtz, 58, was informed earlier this year in a letter signed by Barry and Franklin that his contract, which ends in December, would not be renewed.

"He has been paid for the next four months," Franklin said of Sigholtz. "We thought it was unfair to ask him to stay on top of things during the heavy football season and look for a new job. The board made that decision collectively."

Sigholtz, who has been the manager of the stadium complex for 11 years, said he was told his official duties would end yesterday when Barry called him to his office on Wednesday. Sigholtz said that the complex has never lost money under his management and netted $1.5 million in 1983 out of gross receipts of $5.6 million. He said he was never told why his contract will not be renewed.

"I was just told that they, the board, wanted a change," Sigholtz said. "The mayor explained that it was sort of like coaches who are let go. I said it is not a good analogy. If coaches have a record of 11 and 0, they are usually given a raise and an extended contract."

Sigholtz, a former athletic director at Georgetown University, was named the general manager in April 1973 after the death of manager Arthur (Dutch) Bergman. A retired Army colonel, Sigholtz holds a doctorate in education.

Yesterday, Sigholtz spent the day negotiating with representatives for the Jackson family's Victory Tour. If a contract can be negotiated, the Jacksons would appear in RFK Stadium Sept. 21 and 22, Sigholtz said.

"People have asked me why I'm working like this when I know my contract will not be renewed," Sigholtz said. "I just tell them that I'm a professional and as long as I'm over here, I'm going to do the best possible job. There are no sour grapes."