THE SIDELINES : 2 U.S. Would-Be Medalists Beaten in Amateur Boxing Quarterfinals

American medal hopefuls Terry McGroom and Skipper Kelp were beaten today in quarterfinal matches at the World Amateur Boxing Championships.

The defeats mean that the United States will have only three boxers in the semifinals. Semifinalists are assured of bronze medals.

The 23-year-old McGroom, of Chicago, held his own with Nurmagomed Shanavazov of the Soviet Union in the first round, but the harder-hitting Shanavazov controlled the next two rounds for a 22-9 victory.

Kelp, 18, of Colorado Springs, Colo., appeared lethargic in losing 11-7 to Michael Caruth of Ireland in a slow-paced bout at 139 pounds.

Eric Griffin and Raul Marquez of Houston and Tonga McClain of Racine, Wis., advanced to the semifinals Monday. Griffin will box Kim Dok Nam of North Korea, McClain will box Julio Gonzalez of Cuba and Marquez will meet Francisc Vastag of Romania in bouts Wednesday night.