World Boxing Council heavyweight champion Larry Holmes ripped and clawed his way through the gentleman giant, Gerry Cooney, tonight, scoring a 13th-round technical knockout when Cooney's trainer stepped into the Caesars Palace ring to stop the destruction of his fighter with eight seconds remaining in the round.

Cooney showed a valiant willingness to go on late in the fight, but the unbeaten champion (40-0) was in control after six or seven rounds. A crowd of 32,500 and millions of viewers on closed-circuit television across the nation watched the disassembly of the 6-foot-6 Cooney, who lost his first fight after 25 wins.

Cooney's vaunted left hook shook Holmes early in the proceedings, but the undefeated titlist was patient. He fended off the lefts when possible and began midway through the fight to land successions of left-right combinations that cut Cooney, half-closed his left eye and in the end rendered him defenseless.

The fight seemed destined for infamy in the 10th round when Cooney landed a colossal left uppercut directly to the champion's groin, which doubled Holmes over. But referee Mills Lane stepped in, escorted Holmes to his corner and stopped the fight for over a minute while the champion recovered.

Cooney landed another low blow late in the round that had little effect other than the two-point scoring penalty he was assessed. But when Holmes answered the bell for the 11th, there was fire in his eyes.

He had opened a cut in the corner of Cooney's left eye in the sixth round, and as the fight progressed the eye grew puffier and threatened to close. After the 10th round, Cooney seemed to have trouble seeing Holmes' quick right hand as it rained down upon him with increasing frequency.

Holmes opened the 12th round with a leaping right hand that sent spray flying from the challenger's black hair. He landed a left-right combination to the body that sounded like gunshots, and late in the round sent two left-right combinations rocketing off the challenger's head.

It was clear that Cooney's strength was fading, as his feeble rights and waning left hooks showed no effect on the champion.

In the final round, Cooney landed two lefts to the midsection that Holmes barely noticed. In a neutral corner, Holmes landed a right cross that staggered Cooney and for the next half minute he landed blow after blow to the staggering champion, who lunged after Holmes but was clearly defenseless.

As Cooney reeled along the ropes, Mills stepped in to give him the standing eight count for a technical knockdown. But before Holmes could get to a neutral corner, Cooney's trainer, Victor Valle, had leaped into the ring, raced to his fighter and hugged him, stopping the fight.

The 6-foot-3, 212 1/2-pound Holmes knocked Cooney down for the first time in Cooney's professional career in the second round. A right cross from the champion caught the 225 1/2-pound Cooney on the temple and he went reeling along the ropes just as he did in the final round. But this time he fell in front of his own corner, but was back on his feet after three or four seconds.

It was the first time Cooney hit the floor since he was a 17-year-old amateur.

But the early going was surprisingly even, aside from the knockdown, as Cooney wielded his vaunted left hook with authority and the champion countered with left jabs and straight right hands. There was no question that the challenger's blows hurt Holmes, as he circled and danced to avoid the onslaught of the larger Cooney.

But the left hooks were Cooney's only weapon. His right hand looked amateurish and ineffective and as the fight wore on Holmes' blows seemed to lose none of their effectiveness, unlike Cooney's.

The low blows were a constant problem for the challenger, who was warned against them repeatedly by Lane.

After the fight Cooney told his mother, who was sitting at ringside, "I'm sorry. I wanted to win for you."

She said, "That's all right. I love you." And Cooney's brother Mike was observed after the fight crying unashamedly.

Holmes had said he would defeat the challenger in seven rounds, and after seven he was in increasing control. But Cooney showed determination and the ability to take a punch, and it was six long rounds after that before he caved in.

There was no love lost between these two fighter, who are said to be earning between $5 and $10 million for this fight, probably closer to the higher figure. Holmes felt Cooney, with only 25 pro fights and none against top 10 conternders, didn't deserve a title shot. But at the same time Coooney's popularity with fight fans made this the most profitable fight ever for the champion.

It was Holmes' 12th title defense and the 11th won by knockout.

The Nevada State Athletic Commission, in an unusual move, replaced one of the judges for the Holmes-Cooney fight late Thursday night after Holmes' camp and Jose Sulaiman, World Boxing Council chairman, objected to two judges who had been tentatively chosen.

Judge Herb Santos, whose selection was protested on grounds of inexperience, was replaced by Jerry Roth. Jay Edson, a veteran Nevada referee, said, in his career, which includes refereeing 45 title fights, he had "never heard of a judge being changed at the last minute like this."

The Nevada commission did not replace Dave Moretti, to whom the Holmes camp objected on grounds of inconsistencies in past scoring. Neither camp objected to Lane, the referee, or the third judge, Duane Ford.

Sulaiman said he argued for replacing Santos after requesting records of the last 15 fights that each of the three judges had scored. The commission, he said, was able to produce only seven fights, four of them preliminaries, for Santos. As a result, Sulaiman said he requested the change on grounds of inexperience.

"I would add that I support the Nevada State Athletic Commission 100 percent" on the final selection of judges, said Sulaiman, whose organization sanctioned the fight.

Edson said Roth's credentials "are above Santos'," adding, "With Santos, a lot of the referees here never even heard of him."

Holmes weighed 212 1/2 pounds and Cooney came in at 225 1/2 at the final weigh-in. Like all official functions in the last two weeks of training, the weigh-ins were scheduled separately so the two fighters did not encounter each other.

Caesars Palace arranged separate training sites and struggled to keep all other aspects of the fighters' schedules apart after ugly incidents erupted between members of the two camps early in the prefight countdown.

It worked. At the weigh-in Thursday, Holmes shouted, "I told you seven rounds (before he knocks Cooney out), but if he acts foolish, it won't go four." There were scattered boos from Cooney's supporters, but no Cooney was in sight to respond.

The champion seemed composed and lighthearted. As he stripped off his shirt for his prefight physical, Holmes said, "Watch out, girls." When Cooney's supporters chanted, "Tick, tick, tick"--their fight theme, which implies time is running out on Holmes at age 32--he responded, "You're right. Time is running out--for him."