An American amateur boxing team handed Ireland's national team its first defeat in five years at the frigid and antiquated National Stadium here Saturday night.

The 10-member American team, including a promising fighter from Washington, D.C., left Ireland with seven victories in 10 bouts, just three nights after they put away the British amateur team, 8-4.

Three of the bouts here were stopped by the referee with the American fighters easily ahead. One of those fights featured James Johnson, a 17-year-old junior at Cardozo High School, who defeated Irish featherweight Noel McEvoy.

The referee stopped the fight in the final minute of the third round when a left hook from Johnson knocked his opponent down, blood flowing freely from McEvoy's nose and mouth.

Johnson, who has a 37-10 record, won the 1981 bronze medal in the U.S. national championships and is currently ranked fourth in his weight division in the United States.

Johnson's bout was particularly significant for him because he had been disqualified earlier in the week against the British for keeping his head too far in front of his hands, a move interpreted in amateur boxing as a butt.

"He was pretty strong but I feel as though I just hustled a little more," said Johnson, who boxes at the Burgess Athletic Club in Washington. "I was a little tense . . . and I know I made some mistakes. I just didn't want to make the same mistakes I made in England."

Johnson's biggest problem during the one-week tour of England and Ireland appeared to be with his appetite. "James has a big problem with his teeth -- they won't stop chewing," said Tony Barbero, the assistant American coach.

Johnson was widely quoted here for his explanation of his eating habits. He blamed President Reagan's spending cutbacks. "The way Reagan's been treating us at home, we've got to eat while we can when we're away," said Johnson.

Johnson, who has been boxing since he was 9, says the example of Sugar Ray Leonard inspired him to a boxing career.

"I used to watch Sugar Ray Leonard and Leon Spinks and think, 'One day, I'm going to be there,' and here I am," said Johnson before Saturday night's match. He said he will fight one more year as an amateur before turning pro.

"It's just too long to wait for the Olympics," Johnson said.