Larry Holmes kept his half-championship and Earnie Shavers moved into line for a heavyweight title shot with thundering knockouts tonight.

Holmes, the World Boxing Council's undefeated champion, sent Ossic Ocasio down four times in the seventh round of their scheduled 15-rounder in the Las Vegas Hilton Pavilion. As Ocasio rose a fourth time, the referee stopped it at 2:38.

Shavers needed just under two minutes to separate Ken Norton from his senses. A left hook to the temple sent Norton staggering off the ropes and a neat jab, not all that powerful, caused Norton to fall forward in midring.

A short right 10 seconds later put Norton on his back and the referee didn't bother to count.

As predictable as Holmes' 30th victory was -- Ocasio had only 13 fights, was the smaller man and less gifted -- Shavers' was surprising. Plungers here made Norton a 2-to-1 favorite on the theory that Shavers, at 34, had lost the devastating strength that earned him 54 knockouts in his 56-7-1 career.

Wrong.

"I know Norton was afraid of me," said Shavers who weighed 210 to Norton's 225. "I don't think he was in the best of shape. He took me cheap. I figure the fight would have lasted another two rounds if he was in shape. I'm a puncher and anybody I hit, he's in trouble."

Norton agreed. "He did to me what I was going to do to him," said the man whose reputation rests on losing championship fights to Holmes, Muhammad Ali and George Foreman.

It was 1974 when Norton, 33, a winner in 41 of 46 bouts, last fought a puncher who terrified anyone. Then, Foreman knocked out Norton in the second round, and a similar result seemed certain here tonight when Norton, in a piece of strategy forced on him by his weaknesses, thought to stay on the ropes early.

"Going on the ropes was smart," Shavers said of Norton's move, taking an edge off the compliment by adding, "because he isn't a boxer and he couldn't move."

"I thought I'd catch and counter for two rounds," Norton said, "and then go after him."

By "catch," Norton meant block Shavers' punches with his hands.In practice, the former Marine caught Shavers' punches with his face.

A tentative date of Sept. 14 has been set for a Holmes-Shavers championship fight. That presumes both men safely survive tuneup bouts this summer. Such a fight would be a rematch of Holmes' decisive decision over Shavers last year.

"This time, I'll knock him out," Holmes said after tonight's easy victory. "I am not Ken Norton."

The capacity crowd of 5,376 and a national television audience saw a Larry Holmes at the top of his game. He is 29, 6-foot-3, 214 pounds, the proud owner of a murderous job and heavy right hand.

Although Homes was a heavy favorite against the unbeaten Puerto Rican, 21, who twice beat Jimmy Young to earn this fight, the WBC's champion had to work for his $1.2 million.

Through four rounds, Ocasio, 5-11 and 207, stayed even with leaping counterattacks off the ropes. he also did it because Holmes, clowning in a flatfooted stance at times, seemed bored to tears by the goings-on.

Holmes dominated the last three rounds with the stinging jab and wrecking-ball rights. Midway through the fifth round, when the crowd had fallen silent, Holmes split the air with a scream that, he later said, signalled the beginning of the end for the gallant Ocasio.

Holmes screamed: "Hulk."

That is "Hulk," as in "The Incredible Hulk," the television show in which a mild-mannered frllow, no muscleman, is transformed into a green-skinned Mr. Universe. Anger produces the transformation.

"He hurt me, so I became the Hulk," Holmes said. Anyway, from then on Holmes controlled the fight.

"His style was very awkward," Holmes said of Ocasio's bobbing-and-weaving crouch. "I knew what he was doing, but I had to take time to set him up. I'm the champ. There was no reason to rush in for the kill. I had time to hunt him."

In the last round, a Holmes' jab weakened Ocasio's knee hinges and, 10 sconds later, a jab sent him down. A right cross seemed fully capable of decapitating Ocasio, but instead it turned the youngster's body horizontal. Four times he went down, gamely struggling up each time.

The fight had been stopped before he reached the vertical a fourth time.

"I've been working hard on power with the job," Holmes said to witnesses surprised to see the jab, normally more a defensive weapon than offensive, knock down Ocasio. "This young man took some belluva punches."

Ocasion had never been knocked down.