Dave King defeated Gary Marlowe with a 16-foot birdie putt on the first extra hole in a morning quarterfinal match, and scored another 19th-hole victory with a 22-foot birdie putt to eliminate medalist Eddie Offterdinger in the semifinals of the District Amateur golf tournament yesterday at Argyle Country Club.

King, of Bethesda and Prince Georges, twice a loser in the final of this tournament, will play Randy Morris of Washington in the 36-hole final this morning at 8:30.

"I'm pooped. How do you spell pooped?" said King, 41, after playing 38 holes in four under par in 95-degree heat. Right now I'm going home to relax."

Offterdinger, the medalist from Bethesda, almost holed out a pitch shot from 20 yards to the left of the 18th green. The ensuing five-inch par putt enabled him to halve King on the long par-4 hole and forced the match into an extra hole.

On the par-4 first hole, the 19th, King hit a wedge approach shot 22 feet from the cup and sank the putt to beat Offterdinger, who lay four feet from the cup.

King had hit a wedge second shot on the 19th hole and knocked in the birdie putt to derail Marlowe of Woodmont earlier in the day. Against Marlowe, King played his final 10 holes in four under par.

Marlowe, former Maryland Open and Maryland Amateur winner, was playing in his last area amateur tournament. He intends to play in the Western Amateur in Michigan in early August and then turn pro.

Morris, who learned to play golf on this course and later was assistant pro here, defeated 1973 District Amateur champion Gill FitzHugh of Army Navy in the morning, 2 up, and then was two under par in overwhelming another former pro, Gary Moore of Prince Georges, 5 and 4,