The board of the NAACP today effectively displaced Margaret Bush Wilson as chairman after summarily rejecting as "sour grapes" her detailed and personally delivered argument that executive director Benjamin L. Hooks was an inefficient manager who deserved suspension.

During a four-hour meeting described as cordial in most respects, the board by 49 to 5 reaffirmed its May 28 action repudiating Wilson's eight-day unilateral suspension of Hooks and calling on her to resign the chairmanship.

Last month the board also stripped her of all but ceremonial duties and today went a step further by delegating all her authority to the vice chairman, Kelly M. Alexander Sr. of Charlotte, N.C.

"She has a title, but she can't exercise the prerogatives of that title," board member Nathaniel S. Colley of Sacramento said in explaining the action.

The decision left Wilson, 64, a St. Louis lawyer who has headed the board since 1975 and battled Hooks since 1977, apparently bereft of substantial support but, she said afterward, neither bitter nor surprised.

"I have some reason to believe that they had reached a conclusion that the clash between Mr. Hooks and me was something that they had to deal with," Wilson said. "It's much easier to deal with the messenger rather than the message."

"This is not a conflict between personalities, but a profound encounter about how the NAACP is to be managed," she said. "I have sounded the alarm. It is up to the board to act responsibly."

Wilson said she has not yet decided if she will resign, if she will run for reelection as a board member when her term ends in December or if she will attend the organization's 74th annual convention next month in New Orleans.

Several board members who attended today's meeting at the O'Hare Hilton Hotel said they hoped today's votes would end a bitter, draining and embarrassing fratricidal conflict in the already faltering organization ignited by the May 18 suspension meeting.

"The board feels this will enable the NAACP leadership to devote their energies and experience exclusively to the business of civil rights," Alexander said.

Yet they acknowledged that some of the points raised by Wilson in a 33-page report, billed as an explanation of managerial shortcomings justifying the suspension, deserved further attention--later.

"We did not go into the investigation of all of these charges as to whether or not they were fact or fiction," said board member William Gibson of Greenville, S.C., vice president of the organization. "What we dealt with was the action of the board chairman."

The suspension angered many board members primarily because they were not consulted beforehand and, they said, they did not know of any conditions drastic enough to warrant such harsh unilateral action.

Wilson said in her report today that she did not consult other board members because "there was not time." She acted on her own, the report said, because she feared that Hooks had implied during a stormy May 14 executive committee meeting that he would no longer cooperate with a routine audit of the organization then in its final stages.

Hooks was reinstated at the completion of the audit, at a time when Wilson's action was under sharp criticism by board members.

Most of the report sought to portray the issue as larger than the suspension. It blamed Hooks' management for dramatic decreases in membership, for unpaid bills, high turnover at the top staff level and generally low morale.

It argued that undesirable accounting practices were common and that the management structure concentrated too much authority in the hands of Hooks, his two top aides and his wife, a volunteer. Board efforts to establish checks and balances had been nullified, the report said.

Although it alleged no misconduct, the report did characterize Hooks as a frequently absent chief executive and pointed out that in addition to his current annual salary of $75,000 a year he has earned $360,931 in honoraria from speaking engagements since 1977. Outside earnings are permitted by his contract.

At the end of her presentation, Wilson called for a seven-member committee headed by New Orleans Mayor Ernest N. Morial, a board member, to examine the allegations. The board rejected that proposal.

Asked about the allegations, Hooks told reporters, "I agree with the board--that they were not well founded . . . . The board rejected it as sour grapes and I agree with that."

The Memphis minister said he was glad that "the board had seen fit to put the NAACP back on track--back into the business of civil rights--full time.