For sufficient reasons that need not be recited, the good name of boxing is difficult to defile. But the other day in a South African ring, two clumsy pugilists scuffling for 15 rounds brought insult to the heavyweight picture while fighting for only half the title.

Despite the readiness of the World Boxing Association to crown one of them as its champion, both John Tate and Gerrie Coetzee demonstrated mostly that neither can fight very well. They offered a spectacle sufficient to bring Muhammad Ali back to the wars less than four months after his official retirement.

Big Tate, the 240-pound American, was the winner over the plodding Coetzee, the near-pride of South Africa. But neither man showed anything to suggest he could lick one side of Ali. Tate eventually wore Coetzee down, while proving conclusively that he had no skills with which to put away an opponent who had achieved exhaustion four rounds bfore the finish.

Coetzee dealt repeatedly in righthand leads that would have gotten him cold-cocked by any fighter with basic gymnasium skills. But not by Tate, who was pawing about in the first six rounds and did not assert himself until the ninth despite a clod of an opponent unskilled in getting out of harm's way. Eventually, Tate did get his good licks and the fight was his. And Coetzee got points for courage.

Notes taken on the fight televised by NBC from Pretoria say that it wasn't unitil the sixth round that the most elemental of all punches, the left jab, made an appearance. The notes say: "'none by Tate. This is a contender?" Also, of Tate; "Wearing Ali's white boots and tassles. But Ali, he ain't."

The whole business raised suspicions about the 19-0 record Tate took into the fight and the types he licked. High mark: a knockout of Kallie Knoetze, another South African in Coetzee's mold, but even slower.

From at least one point of view, the fight was refreshing. No blabbering Howard Cosell at the microphone. Nbc offered a new team of Mary Albert as round-by-round man and Dr. Ferdie Pacheco, the old pro and longtime physician in Ali's corner, as commentator. Pacheco rescued Albert often. While Albert in midfight was saying the bout was "very close," Pacheco was strongly suggesting it was very dull. He was also indicating that Tate was winning it. Albert, in Round 11, finally conceded, "The fight so far is very disappointing."

The fight produced more history than it did combat. It shattered apartheid, at least for a day, and fetched 89,000 fans into a previously restricted stadium, some of whom paid $400 for a seat. South Africa hoped this would prove it was now less racist and would win approval from the family of nations, plus perhaps an invitation to the Olympics. This is doubtful.

The clear winners were Bob Arum, the promoter who netted $1 million from the fight and has Tate tied up for three title defenses, and Tate. Much more is in prospect for Tate when he fights Larry Holmes, the World Boxing Council champion who owns the other half of the title, perhaps the most important half.

A certain accommodation between Arum and Don King, the rival promoters who hate each other, is in the offing. King has Holmes under contract and says the WBC title is more important than Tate's WBA crown. The prospect of making a big score from networks bidding for Holmes-versus-Tate is certain to sooth the animosity of Arum and King. Remembered is Voltaire's line: "When it comes to money, everybody is the same religion."

But it is a dismal era for heavyweights. Lacking an Ali, who could whip up a frenzy at any time, there is no charisma in the division. Holmes, who has sometimes given signs of being a complete fighter, has also showed a tendency to become fat and lazy. In that condition, he had a hard time with nondescript Mike Weaver earlier this year. And Earnie Shavers almost took him out with one punch before spending himself in one glorious round.

Right now, there is nobody of substance beneath Holmes and Tate who, of themselves, are not compelling gate attractions. Those two will get a big payday from a network when they do fight, but there is little else in prospect to sustain the heavyweight division.

Whereas promoter Arum bought the Tate-Coetzee package for a total of $700,000 for both fighters, it is of inescapable memory that the last previous big heavyweight fight in Africa, Ali vs. George Foreman, commanded a purse of $8 million. Without Ali, it's not the same.

A renaissance of a suprising nature has, in fact, taken place in boxing. Excitement has shifted away from the heavyweight division. The welterweights, once scorned as mere preliminary fighters on heavyweight title cards, are in the ascendance. For his title fight coming up Nov. 30 with welter champ Wilfredo Benitez, the unbeaten Sugar Ray Leonard will get a $1,200,000 payday.

It is Leonard, the fancy dan with knockout skills, who has generated the great new popular excitement among the welterweights. And he is merely a challenger. The division has two certified champions in Benitez, the Wbc titleholder, and Jose Cuevas, the more exciting WBA champ. And with knockout artist Roberto Duran looking over the shoulder of all of them in his own quest for the welter title, it could be said that the division is humming while the heavyweights can contemplate their own dreary times.