* McGirt shoots eight-birdie 65 to take control
* Americans McNeill and Beljan tied for second
* Eleven players within four of the lead (Adds detail, quotes)
By Mark Lamport-Stokes
PACIFIC PALISADES, California, Feb 15 (Reuters) - Little known American William McGirt, seeking his first PGA Tour win, broke clear of a congested leaderboard to seize a two-shot lead in Saturday's third round of the Northern Trust Open.
Two strokes off the pace when the delayed second round was completed earlier in the day, the 34-year-old journeyman took advantage of several favourable pin positions with superb all-round golf to fire a six-under-par 65.
McGirt birdied five of his first six holes, then picked up three more shots in the first four holes after the turn on the way to a 12-under total of 201 in the PGA Tour event at a firm and fast-running Riviera Country Club.
"Played really solid, hit a lot of good iron shots and good putts," McGirt told reporters after mixing eight birdies with two bogeys on a day of hazy sunshine and occasional cloud cover. "Just one of those days you could see the line.
"On the putting green, my stroke felt fast and I've been working hard trying to slow it down. Nothing felt good warming up, the putter didn't feel good and the swing really didn't feel good.
"Maybe there's something to it," McGirt said with a broad grin. "I hit a lot of good shots and starting out, the hole looked like a washtub. All in all, it was pretty good all day."
George McNeill, a double winner on the U.S. circuit, carded a 66 after eagling the par-five first to finish at 10 under, level with fellow American Charlie Beljan (68).
Two more Americans, left-hander Brian Harman (68) and Monday qualifier Jason Allred (67), were a further stroke back in a tie for fourth.
Eleven players were within four strokes of McGirt's lead, including former Masters champions Bubba Watson (64) and Charl Schwartzel (68), multiple PGA Tour winner Dustin Johnson (69) and 2013 PGA Tour rookie of the year Jordan Spieth (67).
"This is what we strive to do, have a chance on Sunday," American left-hander Watson said after piling up seven birdies in a bogey-free display to finish four off the pace. "I'm looking for the back nine tomorrow, having a chance.
"You don't want to come to the back nine going, 'Well, if I shoot 30, then I still don't have a chance to win.' I want that chance to win going into the back nine tomorrow."
South Korea's Bae Sang-moon began the third round with a one-stroke advantage and he maintained that with a birdie at the par-four first before falling back with bogeys at the fourth and eighth.
Five players held at least a share of the lead early on before McGirt stormed three strokes in front with birdies at the 10th, 11th and 13th, where he sank a 10-footer.
Though McGirt recorded a three-putt bogey at the 15th to slip back to 12 under, he parred the last three holes to preserve his two-stroke cushion atop a crowded leaderboard.
McGirt, who has twice been a runner-up on the PGA Tour but had not made the cut at Riviera in his two previous starts, had a simple strategy in mind for Sunday's final round.
"It's just 18 more holes and whatever is going to happen is going to happen," the 34-year-old said. "All I can do is go out and play the best I can."
Asked to explain why he had flourished at Riviera this week after missing the cut in 2011 and 2013, McGirt replied: "The big thing is the golf course is playing much faster and getting some run and the ball can carry.
"It's probably 15 degrees warmer than I've played it here ... and so the ball is kind of chasing a little bit. That helps me out a bunch." (Reporting by Mark Lamport-Stokes; Editing by Gene Cherry)