Sugar Ray Leonard said yesterday he outgutted Roberto Duran on a full stomach that raised his weight by four pounds the day of the fight and that he, too, had cramps that affected him after the bout.

After a news conference at the Sheraton Inn, New Carrollton, the World Boxing Council welterweight champion disclosed that besides having weight problems for both bouts with Duran, he missed three days of training for the rematch with a virus that "knocked me out," and took diet, or so-called "water pills," on his way to the 1976 Olypics.

"If I had lost to Duran (on Nov. 25) would you have believed me if I said afterward that I had a headache or hemorrhoids, and couldn't move? Excuses are for imcompetents."

After 23 rounds in the ring against Duran and several encounters elsewhere, Leonard acknowledged that he felt he knew the working of Duran's mind. He was asked if he thought the former champion might have tried to taint Leonard's triumph by quitting, once he detrermined he could not beat him.

"No," Leonard said. "I don't think he's that bright. I think that he had built such a personal hate of me that when he found out I was going to outsmart him at everything he tried he said to himself, 'I'd rather quit than Let Sugar Ray Leonard knock me out or humiliate me.'

"He had said, 'I'm going to finish Leonard this time (second bout), destroy him, knock him out.' But all of a sudden, in this bout, every time he expected me to do something he had seen in our first bout, I did something different. Every time he tried a motion that didn't work I hit him. He reacts to the crowd and that bothered him.

"I do, too. When I got in the ring I reacted to shouts of 'Sugar Ray . . .. Sugar Ray.' I got further charged up when I met Ray Charles for the first time in the ring. You know I was named for him. We hugged and that motivated me more. It was a package deal.

"If Duran had cramps, why didn't he double up? Cramps doesn't make any sense. After the fight he showed no signs of cramps, like when we embraced."

On the day of the fight, Duran said he consumed beef broth, two steaks, orange juice and tomato juice and ate fruit at 1 p.m. and another steak and eggs and fruit juices at 4 p.m.

Leonard said yesterday, "I weighed only 140 pounds at the end of the first bout in Montreal, and that cost me strenght. I was determined to weigh more this time. After I weighed in at 146, at 1 p.m. I ate three scrambled eggs, greens, grits, boiled fish, biscuits, canned peaches, and Kool-Aid. I wanted to weight 150 pounds. At 4 p.m. I ate leftover fried chicken, two slices of bread, apples, oranges and tangerines, and drank more Kool-Aid.

"I had cramps after the fight, gas from a nervous stomach. Duran wasn't on schedule with his cramps," Leonard said, grinning at his taunt.

He said he took diet pills as an amateur on his way to the Olympic Games "because I was putting on weight so fast." He won the gold medal as a light welterweight (139 pounds). Muhammand Ali has attributed his loss to Larry Holmes to the use of diet pills. Duran reportedly used them to reduce his weight from 170 in early September to the 147-pound welterweight limit for the rematch.

Leonard said he was stricken by a virus on Oct. 21, when he began training here. "My lungs were congested," he said. "My body ached. I went to my doctor and he gave me pills, but I couldn't run or work out for three days. People were saying I was missing training and when I resumed they were saying I wasn't looking good, and some were still saying that down in New Orleans. I heard them say I wouldn't move."

The inevitable question or retirement came up after Leonard said there would be no third bout with Duran, even if he redeemed himself in other bouts, "because it would not be in the best interest of boxer's integrity."

What would he concentrate on, now that he doesn't have Duran as an incentive?

"Right now, I'm concentrating on an expansion of my family. Then I will concentrate on the winner of the Tommy Hearns-Wilfred Benitez bout (for the World Boxing Association title on Feb. 21). Hearns will motivate me, if he wins. He tries to get at me like Duran did before our first bout. Hearns threw a rubber chicken or a rubber duck at me at my news conference after I beat Duran. Hearns sticks in my craw."