Defending champion Jim Furyk scorched into a four-shot lead in the $4.3 million Nedbank Challenge as Padraig Harrington failed to sparkle.

In a second round delayed by nearly three hours dues to lightning, defending champion Furyk kept a vice-like grip on the title with a sensational 66.

Four clear of Henrik Stenson on 10 under par, Furyk has yet to make a bogey in his bid for the €1.2 million Sun City showdown.

But it was a hard day in the jungle for Harrington, who again dropped two shots coming home to slip six behind the ice-cool American.

Out in three under par, Harrington was never fully in control of his game and bogeyed the 12th and 18th on his way to a one under par 71.

But it could have been a lot worse, especially after a visit to the deep rough off the 14th tee at the Gary Player Country Club.

Buried in deep rough down the left, Harrington slashed his way as far as the cart path but did not get to salvage a par until nearly three hours later due to the weather delay.

His late bogey relegated him into a share of fifth place with Retif Goosen and Trevor Immelman on four under and still well in the hunt.

But the Dubliner's round looked a little ragged compared to the controlled play of Furyk, who putted brilliantly again to rack up six birdies.

Overnight leader Stenson lost ground with a 71 but was still Furyk's biggest challenger at the end of a day that saw Ernie Els storm into a share of third place with Charl Schwartzel after a 67.

In contrast to the first round, Harrington missed eight greens and did well to be three under for his round after 10 holes before those back nine bogeys made his weekend task tougher.

It was a day to forget for Scot Colin Montgomerie, who ran up a quintuple bogey nine after hitting the trees three times at the par-four 11th.

A birdie at the last gave him a round of 77 but still left him propping up the scoreboard on eight over par.

Leaderboard (par 72)

134 Jim Furyk 68 66;
138 Henrik Stenson 67 71;
139 Ernie Els 72 67; Charl Schwartzel 70 69;
140 Retief Goosen 70 70, Padraig Harrington 69 71, Trevor Immelman 71 69;
142 David Howell 69 73;
144 Jose Maria Olazabal 71 73;
148 Sergio Garcia 72 76;
149 Chris DiMarco 74 75;
152 Colin Montgomerie 75 77.