McDowell had double bogeys on the 10th, 11th, 17th and 18th holes. He posted just three birdies in the second round.
"It's not the way I wanted to play the last couple of days," he said. "But this place is very hard."
PAN'S MOVE: The surprise of Friday's play at the U.S. Open were a pair of amateurs — Michael Kim of Cal and Cheng-Tsung Pan of Taiwan. They were 2 under for their round and among those who didn't finish.
Pan must finish his round Saturday morning. He had two birdies and no bogeys to zip into a tie for third place at even par. Kim is 1-over so far and tied for eighth.
Pan, a 21-year-old from Taiwan, is a junior at the University of Washington. He missed the cut in his other Open appearance in 2011, saying he was too excited and had too many distractions to play his best game.
This time, Pan said he embraced the pressure that comes along with a major.
"I feel I belong to that kind of place," he said. "I'm not saying I'm good enough, but I love this kind of feeling and the competition is great. I just want to be here always."
DONALD'S DAY: Luke Donald holed out a chip for birdie on the short par-3 13th to reach 4 under and top the leaderboard in the U.S. Open.
Not for long.
He bogeyed Nos. 4-7 to totally spoil his round Friday. Donald was at 4 under Thursday before play was suspended, and finished with a 2-under 68 on Friday. He added a 72 in the second round to leave him even par for the tournament.
The English star had a run of five bogeys in six holes on his back nine in the second round.
"The greens have been tricky to read all week," he said. "They seem to be breaking a little bit more than I'm seeing, hence a couple of lip outs. But you try not to panic in U.S. Opens."
Donald, playing in his 10th U.S., has never won a major. The former world No. 1 played a pair of practice rounds last week at Merion to get used to the course. He even posed for a photo with David Graham, winner of the 1981 U.S. Open at Merion.
"I asked him, 'What's the secret?'" Donald said. "And he said, 'Keep it in the short stuff.' Obviously, I think most of us know that and it's all about doing it."
The 35-year-old Donald failed to make the cut last year in the U.S. Open at the Olympic Club in San Francisco because of putting failures. He has never finished better than 12th in an Open (2006) and missed the cut three times since his 2002 debut. He was 45th in 2011 and 47th in 2010.
Donald and Lee Westwood are the only players to be No. 1 without having won a major.