The prospect of winning a $3-million horse race must keep a man young.

Fred W. Hooper, age 87, was at Hollywood Park early this morning to supervise the training of his horses, in particular Precisionist, who is a strong contender to win the Breeders' Cup Classic on Saturday. He is as energetic, opinionated and stubborn as he has been all his life.

To people in the racing community, Hooper's defiance of the laws of geriatrics is less amazing than his performance as an owner and breeder. He is the very prototype of the overbearing, meddlesome owner who drives trainers crazy and usually makes a mess of everything.

Except that Hooper keeps winning and winning, defying all logic. He won the Kentucky Derby with the first horse he owned, and now he has an excellent chance to win the richest horse race ever run.

Hooper learned about horses growing up on a farm in the West; before there were tractors, horses did the work. His father also kept some horses for sporting purposes, and Hooper still remembers that one of them won 49 races, mostly match races with horses from other farms. That got him hooked on the game at an early age.

But Hooper wasn't cut out to be a farmer himself. He tried once, operating a farm in Florida, and when a fungus destroyed his potato crop, he said, "I went completely broke." He went to the banker whom he owned a considerable amount of money and announced, "You're looking at a contractor now."

Hooper bought some heavy equipment on credit, started a construction company and began paving roads in Florida. Eventually he was building highways, dams and airport runways throughout the Southeast, and he had the wherewithal to indulge his boyhood passion.

He went to a sale intending to buy some broodmares to start a small breeding operation, but he wound up buying a yearling colt, too. "He caught my eye," Hooper recalled, "and I said, 'I'm going to own him.' " The price was $10,200 and the horse was Hoop Jr., who won the 1945 Kentucky Derby.

For four decades Hooper's familiar red and blue colors have been a prominent part of racing in the United States. His colt, Olympia, possessed almost legendary speed, and became one of the country's most influential stallions. His mare, Susan's Girl, was a champion. And now Precisionist has developed into one of the top horses of 1984, even though he does not yet have much of a reputation outside the West. In July he won the Hollywood Derby by 10 lengths. In his last start, the $500,000 Super Derby at Louisiana Downs, he set a swift pace and Gate Dancer had to shatter the track record to beat him by a head.

All these horses have Hooper's imprint on them. He breeds all his own runners; he doesn't spend his money at yearling sales for other people's pedigrees any more. When the great Susan's Girl was retired, he could have bred her to any illustrious stallion in the world. Instead he bred her to his stallion, the relatively unsung Tri Jet. This might be crazy, but Hooper was voted the outstanding breeder in the United States in both 1975 and 1982.

If he is opinionated about the subject of breeding, Hooper is no shrinking violet on the subject of training, either. "I know a lot of trainers don't want owners around," he conceded, "but as long as I've got the money invested, I'm going to have something to say." His current trainer is young Ross Fenstermaker, but Hooper's tall, lean figure is a familiar presence at the stable.

The fortunes of many other stables have been spoiled because an owner wouldn't give his trainer a free hand, but it's hard to question a man who has been winning for 40 years and may still have his greatest victory ahead of him.

"I've always tried to get to the top of the ladder," Hooper said, "and I guess a $3-million race is the top."