Mark Kim of Chartwell Country Club upset defending champion Mike Hoss of Evergreen Country Club, 5 and 3, in the third round of the Bobby Bowers Junior Memorial Tournament at Springfield Country Club yesterday. Kim then advanced to today's semifinals with a 1-cup decision over Joe McCardle, of Springfield.

Kim, medalist in last week's Maryland State Junior Championship, led Hoss by one at the turn and played the next six holes at two under par to win the match on the 15th green. Kim was two over on the front, but birdies on 14 and 15 put him even par for the round.

In the afternon quarterfinal match, Kim was three up on McCardle at the turn but lost three holes on the back nine before rebounding to win on the last green.

Mike Echols, of Charlottesville pulled off the other morning upset when he beat Ed Lupton of Midlothian, 1 up. In quarterfinal play, Echols survived a 20-hole test with Mike Price of Johnstown Country Club. e

Price put his second shot in a trap and three-putted for a bogey-6. Echols reached the green in regulation and putted for par to win.

Echols meets Danny Derisio of Springfield Country Club in the semifinals at 7:30, while Bob Kramer of Pinehurst Country Club, who has never played a matchplay tournament. The winners meet in the finals at 1:40.

Matt Bowl of Fredricksburg recorded the six-year tournament's first hole-in-one yesterday. Bowl dropped in his 196-foot tee shot into the 13th cup using a five-wood, but still fell to Brain Lenhard of Evergreen Country Club, 2 and 1, in the third round of the 14-15-year-old division.