Jim Liu

Meanwhile, two-time U.S. Open qualifier Beau Hossler, 17, of Mission Viejo, Calif., was eliminated in the second round.

Liu defeated Eric Ricard, 17, of Shreveport, La., 3 and 1, in the afternoon’s third round. In the morning’s second round, he defeated James Riley, of Hattiesburg, Miss., 2 and 1, on the strength of seven birdies.

“It was a long day,” Liu said. “I played really well this morning and didn’t really expect to play well this afternoon, but that’s what happened.”

Hossler lost to Andrej Bevins, 17, of Elk Grove, Calif., 4 and 2.

“Andrej played great,” said Hossler after his defeat. “I left a lot out there, there’s no doubt.”

With Hossler out, Liu and Nicolas Echavarria, 17, of Colombia become the most well-known players remaining. In 2010 Liu, at 14, became the youngest champion in Junior Amateur history, breaking a record held by Tiger Woods. Echavarria and Liu tied with Shintaro Ban of San Jose, Calif., for medalist honors in the stroke-play qualifying portion of the championship.

Liu was 1 up at the 176-yard, par-3 14th hole when he matched Ricard, who ran in a 40-foot birdie putt, with his own 6-footer to halve the hole.

“That was a good time to help my confidence, coming in,” Liu said.

Liu won the 15th hole with a par to go 2 up and birdied the 17th to win the match.

“There was a little bit of pressure but it doesn’t make that much difference because we were having so much fun out there,” Liu said.

Echavarria, a 2011 semifinalist, defeated Charles Cai, 17, of West Windsor, N.J., 1 up, to reach the final eight.

Andy Hyeon Bo Shim, 17, of Duluth, Ga., eliminated Bevins on the 19th hole to make the quarterfinals.

“I didn’t miss a single putt on the front side inside of 10 feet,” Shim said. “I made all of them.”

Shim was forced to make a 6-footer for par, and Bevins a 5-footer, to halve the 17th hole. They halved the 18th with double-bogeys and went into extra holes. Shim made a 25-foot birdie putt on the 19th to end Bevins great run.

Joo-Young Lee, 17, of Hilliard, Ohio, endured affliction and muscle cramps to win his match against Zachary Bauchou, 16, of Forest, Va., 3 and 1. On the ninth hole, Lee was allowed to stop for five minutes of stretching under The Decisions on the Rules of Golf when he was stricken with severe cramps. He has also been battling mononucleosis for three months.

“I honestly don’t know how I did it,” Lee said of his win. “What’s in orange juice, vitamin C? I drank a lot of that stuff.”

Maverick McNealy, 17, of Portola Valley, Calif., defeated Zecheng Dou, 15, of the Peoples Republic of China, 3 and 1, to advance to the quarterfinals. McNealy trailed in the match until the eighth hole and went ahead for the first time with a birdie on the ninth.

McNealy has trailed in most of his matches this week.

“I don’t want to say I’m getting familiar with the position, but I’m getting used to it,” McNealy said.

Reinforced by two peanut butter-and-jelly sandwiches, a banana and four energy bars, McNealy went 2 up with a birdie at the 15th hole. Still 2 up at the par-3 17th, McNealy hit a wedge to within 3 feet of the hole and was conceded the birdie and the win.

“I am so excited, this is awesome,” McNealy said. “I’m having the time of my life.”

Nicolo Galletti, 17, of Pleasanton, Calif., defeated Douglas Ghim, 16, of Arlington Heights, Ill., 3 and 2. Galletti’s opponent in the morning’s second round, Vincent Whaley of McKinney, Texas, who went to the sidelines, 2 down, was his caddie, a deal the two friends made earlier in the week.

“It helped a lot to have a caddie who knew about the game,” Galletti said.

Also advancing was Matthew Scobie, 16, of Canada, who defeated Tae Wan Lee, 17, of Korea, 3 and 1. Branson Davis, 17, of McKinney, Texas, defeated Richard Hattori, 16, of Honolulu, Hawaii, 1 up. Hattori was 3 up when he and Davis both hit into a water hazard on the eighth hole. Davis won the hole with a bogey, pulled to within a 2-hole margin and said it was the turning point of the match.

“I felt like I was right back in the match,” Davis said. “I went from thinking I could be 4 holes down to being 2 holes down.”

In Friday’s quarterfinals, Liu will play Galletti and McNealy faces Scobie. Echavarria will play Davis and Lee goes against Shim.

Semifinal matches will be played in the afternoon and the Junior Amateur, one of 13 national championships conducted by the United States Golf Association, concludes with a scheduled 36-hole final on Saturday.

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