The executive board of the Teamsters union today unanimously installed Jackie Presser, 56, head of the Ohio Teamsters, in the hot seat of the union's presidency.

The feisty, media-minded Presser will bring a more colorful style to the No. 1 job in the nation's largest, wealthiest, most powerful and, by repute, most corrupt union. But his ascendancy probably also assures that the union will stay in the eye of federal investigators, because of continuing allegations that he is linked to organized crime.

Graying and chubby in a well-tailored suit, Presser wore a cherubic smile as he repeated the oath of office before a phalanx of cameras and exchanged compliments with the man who swore him in, his former rival for the post, Secretary-Treasurer Ray Schoessling.

The man Presser replaces, Roy Lee Williams, who stands convicted of conspiracy to bribe a U.S. senator, was not mentioned in the perfunctory ceremony.

Addressing the TV cameras, Presser pledged to take the union in a "progressive new direction." Referring to the membership he said, "Our actions will make you proud again--proud to be Teamsters."

The top Teamster post has long been the Darth Vader chair in the American labor movement. Three of the union's last four presidents have done time in prison.

Arguing that the dirty image of the Teamsters is at least partly unfair, Presser said, "While investigations have continued through the years, I am confident--and I do mean confident--that this chapter in our long 80-year history is coming to a close. These investigations have found no other evidence of wrongdoing, and no indictments have ever been entered into against me let alone have I ever been recommended for indictment."

He asked that people "judge me accordingly by my performance and my actions." He said he intends to "be accessible and will run an open, honest administration." In return, he asked the press for a "fair shake."

In marked contrast to some of his tight-lipped predecessors, Presser seemed to bask in the limelight, fielding hostile questions with zest.

Presser until today earned around $300,000 annually from his union positions, including the leadership of the Ohio Conference of Teamsters, the presidency of Local 507, and the presidency of Joint Council 41. That will now rise to nearly $500,000 a year plus expenses, his aides said.

An eighth-grade dropout who began his career as a jukebox delivery boy, Presser learned the tricks of the trade at the knee of his father, Cleveland Teamster boss William Presser, who kept his son at work in various union jobs.

The senior Presser, who died in 1981, was convicted three times, of contempt of Congress, destroying subpoenaed evidence (a payoff list) and misusing $590,000 in Teamster funds. He served two brief prison terms.

Jackie Presser is a client of the high-powered Washington public relations firm of Robert Gray. He is expected to make wide use of modern mass communications. "He is impressed with mass communications and he is a great communicator," said one of his public relations consultants.

In the mid-1970s, ever image-conscious, he lost 100 pounds of his 300-pound bulk.

In 1980, Ronald Reagan made a general election kickoff appearance before Presser's Ohio Teamsters, and for the first time used the word depression to describe the nation's economic plight.

It was Presser who in 1981, at an executive board meeting at California's La Costa Country Club, reportedly delivered the impassioned speech that resulted in a unanimous endorsement for Reagan, the only major labor endorsement he got. The administration, in turn, named Presser to its transition team and Reagan's inaugural committee.

However, this sudden limelight brought into high relief an accumulation of charges against the Cleveland Teamster leader.

Presser's Cleveland lawyers, the Climaco brothers--John Rocco and Michael --were omnipresent at poolside or in the hotel's breezeways here this week offering detailed rebuttals of accusations made by forces ranging from law enforcement officials to Aladena James (Jimmy the Weasel) Fratiano, former acting Mafia family boss, killer, and the highest-ranking mob member ever to turn government witness.

Presser prefers to focus on his plans to bring the union into the "new America," with aggressive organization in white-collar, technical and public sector fields, to expand programs for retired Teamsters and other services, and to step up the fight against trucking deregulation.

Dissidents have said Presser, as a bargainer, is soft on employers. "You might as well let the trucking association be the head of the union," said dissident spokesman Ken Paff. "They'd have the same problems and steal less money from us."

The Teamsters union has around 1.7 million members, not only in trucking but, as one official put it, "We represent everyone from airline pilots to zookeepers."