Reigning Masters champion Tiger Woods, chasing a record 83rd US PGA title, and Rory McIlroy, trying to become world number one, struggled Friday while Ryan Palmer seized the lead at the Farmers Insurance Open.

Woods overcame a double-bogey disaster on the first hole to shoot a one-under par 71 while McIlroy faded late to fire a one-over 73, leaving both on four-under 140 and six adrift of Palmer's pace after 36 holes at Torrey Pines.

"It played a lot harder for everyone than yesterday except for Ryan -- he's the only one who figured it out," Woods said.

Palmer shot 62 on the North Course, one of two being used on the first two days, to stand on 134 and grab a two-stroke lead over fellow American Brandt Snedeker, who fired a 67 on the South Course at the San Diego layout.

"It was one of those days where I knew the scores were low, I knew I could get a nice round in there if I could get the putter rolling and I did," Palmer said after firing 10 birdies and a closing bogey. "It's exciting. I love where my game is at and I'm excited for the opportunity."

Woods, a 15-time major winner playing his first event since turning 44 last month, seeks his ninth career crown at Torrey Pines, having won the 2008 US Open and seven US PGA titles at the famed San Diego layout.

Woods matched Sam Snead's US PGA record of 82 career wins with a victory last October in Japan and this is his first attempt to seize the mark alone.

But his cause took a major blow when he four-putted the first hole, botching two short par putts.

"I tried to ram it in the hole and it bounced out," Woods said. "I hit a terrible third putt.

"I hit a lot of good shots. I'm driving the ball better, which is nice. In the middle part of the round I made those putts."

Second-ranked McIlroy, who returns to the top for the first time since 2015 with a victory.

Palmer opened with back-to-back birdies, managed the trick again at the fifth and sixth holes and birdied the par-3 eighth as well to climb the leaderboard.

On the back nine, Palmer began with back-to-back birdies, repeated the feat at 13 and 14 and closed with birdies at 16 and the par-5 17th before his bogey at 18.

Tiger Woods fired a one-under par 71 in Friday's second round of the US PGA Farmers Insurance Open
Tiger Woods fired a one-under par 71 in Friday's second round of the US PGA Farmers Insurance Open GETTY / Sean M. Haffey

"I made a good 5-footer to save bogey. It was awesome," Palmer said.

"It's a hard golf course and the patience you're going to have to have is going to play a key role. The way I'm driving the ball gives me a lot of confidence for the weekend."

Woods rolled a two and a half foot par putt past the cup at one and botched a comeback bogey attempt from twice as far, clinging to the cut line at 1-under.

Woods blasted from the rough to two feet and birdied the par-5 sixth hole, made a tense six-footer for par at the seventh, then dropped his approach seven feet from the pin and birdied the par-3 eighth.

He holed out a 15-footer from the fringe for a birdie at the par-5 ninth, then sank a five-footer at 10.

Woods found a bunker off the tee at the 12th and missed a seven-foot par putt to stumble back then hooked his tee shot at 17 and needed a clutch five-foot putt to save bogey.

At 18, Woods reached greenside rough in two, then sank a five-foot birdie putt.

"It was a good middle part of the round. Made a mistake that cost me a shot but made a birdie at 18," Woods said.

"It's a marathon. it's a long haul. I'm just going to try to be there at the end and see what happens."

McIlroy, a four-time major champion from Northern Ireland playing on the South Course, sank a 16-foot birdie putt at the seventh and tapped in for birdie after a 10-foot eagle miss at the par-5 ninth.

But McIlroy missed a five-foot par putt to bogey the 12th, took another at 15 and hit two bunkers to bogey 18.