D.A. Weibring shot a 63 on Friday

Mason, the 1994 Scottish Open champion, shot a bogey-free six-under-par 64 to move to 131 at the halfway stage - nine-under par.

American D.A. Weibring posted a day's best 63 to move within a shot of Mason on the leaderboard.

Weibring, a five-times PGA Tour winner, began the day on one under par but finished on eight under after a scintillating round that included eight birdies and just one dropped shot down the last.

Fellow American Bruce Summerhays, who shot a blemish-free round of 65 to go with his opening 68 and lies at seven under par.

TURNBERRY LEADERBOARD (GB&Ire unless stated) -9 C Mason -8 D A Weibring (US) -7 B Summerhays (US), T Watson (US), T Kite (US)

Overnight leaders Tom Watson and Tom Kite both dropped shots early in their second rounds but recovered to stay in contention.

Five-time Open winner Watson carded a 67, which included an eagle at the par five seventh hole, to lie at seven under par.

Kite matched his old rival for the second day running.

"With so little wind about, I knew today was the day to go low," said Weibring.

"I started well with three birdies in my first seven holes and then kept it going nicely.

"It was a shame to drop a shot at the last but that's not going to spoil my day."

Former Masters and US Open champion Fuzzy Zoeller shot a 69 to go with his opening 67 and lies at four under par for the tournament.

American legend Jack Nicklaus, playing with Watson and Mason, moved up the leaderboard with a 67 to lie at three under.

Defending champion Noboru Sugai has fallen back to level par after a round of 73.