Nineteen-year-old Gary Marlowe of Rockville shot a 66 yesterday for a one-stroke lead on the first day of the rain-shortened Maryland Open Golf Championship at Manor Country Club.

Late afternoon thundershowers forced suspension of play with 71 of the 179 starters still on the course. Play will be resumed at 8 a.m. today with players beginning from where they were halted.

Marlowe, a 1977 graduate of Good Counsel High School who plays out of Woodmont, birdied six holes and had just one bogey, on the 13th hole. He required only 28 putts.

Finishing one stroke behind Marlowe was Bruce Lehnhard of Evergreen, who birdied five of the final seven holes and, like Marlowe, shot a 32 on the back nine.

"My putting was mediocre," admitted Lehnhard, who finished 11th in last year's Open. "The only thing that saved me was that I was hitting the ball close to the hole."

Lehnhard missed three putts for birdies inside of 10 feet. "The way I've been playing, I'm happy with anything I shoot," summarized Lehnhard.

Mark Diley, a pro at the University of Maryland course, shot an eagle 3 on the 424-yard 14th to finish the first round of the 54-hole tournament with a 68.

One threat to the early leaders could be Mark Alwin of Woodholme, who was six under par on the 14th tee when rain suspended play.

Two other pros equaled par 70; Luther Showaker of Fernway and Al Green, unattached.

The field will be cut to the low 60 scorers and ties after the first round; at the end of the second day, the low 40 and ties will continue.