Sugar Ray Leonard won his 14th consecutive professional fight yesterday with a technical knockout victory of Floyd Mayweather in the final minute of a 10-round welterweight fight.

Leonard swarned over Mayweather for the last eight rounds, pounding the Detroit native with overhand rights and body punches. Mayweather was knocked down twice in the eight round.

This was Leonard's first encounter with a world-ranked welterweight. Mayweather, rated No. 17 by the World Boxing Council, said, "I was staggered throughout the fight but I just kept going.

"I was knocked down once, twice, three times . . . I'm not sure but I know I couldn't finished. They shouldn't have stopped the fight on that tittle flurry at the end."

"I thought I looked pretty good," said Leonard of Palmer Park, Md. "I kept setting him up for the left hook all day. He was flashy and had quick hands, but I wore him down as the fight went on."

Leonard's final onslaught had Mayweather out on his feet, groping across the ring and holding on to the referee. If Leonard showed any weakness today it was in his inability to stalk and destroy a wounded foe.

Many times throughout the fight Leonard had Mayweather against the ropes, covering up. Leonard would bang his right hook to Mayweather's side, then slam him with overhand rihts by the half dozen. But Leonard could not create the opening for a clean knockout punch, though at least five good left hooks had Mayweather's knees wobbly.

"Ray fought against a good pro," said Angelo Dundee, Leonard's manager. "Ray went to school today. He had to club-fight this guy, take charge of him and run the fight."

Mayweather claimed that he had injured his right wrist in the first round and never was able to punch with authority. "I could have done better if I had two hands." said Mayweather, whose records now is 15-2. "I still don't know how tough Leonard is because I couldn't fight like myself.

"He's a fairly decent puncher," said Mayweather. No. 6-ranked U.S. welterweight by Ring Magazine, "but he's no kayo artist. A surprise shot of his might take you out. And he might get you with a flurry. But he can't really punish you if you see it coming.

"As this Leonard moves up the ladder trying to get the title, he's gonna meet a lot of people like that."

Leonard showed his customary showmanship, or hot-dogging, depending on taste, in this nationally televised fight. He weiggled his hips, gave his imitation of a bolo punch, and generally clowned whenever the action slowed and the smallish crowd of 4,000 became restless.

As in several previous fights, Leonard fought best when his opponent was fresh, then had trouble concentrating once he knew the bout was well in hand.

"I sure nailed him with a lot of right hands to the same spot on the side of his head," said Leonard, who must have counted that spot 200 times. "As a human, I kinda felt like the fight should have been stopped in the sixth. A guy shouldn't have to stay in there and just get banged around."

However, until Leonard learns that precise and sudden art of the knockout, he will be faced with these arduous and lengthly executions.

Of Leonard's 14 pro opponents, Mayweather was the first who had a classic fighter's physique.

However, tough and experienced as the 24-year-old Mayweather was - adept at holding, grabbing, raking with the laces - he was in constant trouble from the late third round on.

Leonard's knockdowns in the eighth came in quick succession. A clean left hook drove Mayweather backward across the ring with Leonard swarming, both hands hooking, until his opponent was on the seat of his pants for an eight count.

Seconds later Leonard had driven Mayweather to one knee again with a flurry of head-hunting hooks. But Mayweather, as he did repeatedly, covered up in the corner and survived the round.

Mayweather, holding his head in the right hand which did not appear seriously injured during the fight, finally gave his conquerer some of his due. "Yeah, he's the toughest I've fought," said the quick-handed Mayweather. "I'd like to fight him again . . . but there is no doubt, he's a contender."