Californian Roger Maltbie, the product of a 1944 marriage between a Scotswoman and a U.S. flier stationed here during the war, today took a precarious midway lead in the 106th British Open golf championship.

Maltbie, whose parents are with him here for a sentimental one-month visit, shot a four-under-par 66 for a 36 hole total of 137. Not bad for a fellow playing on seaside links for the first time, but one stroke behind him is a foursome with considerably more mjor-tournament experience.

Bunched at 138, two under par, are Jack Nicklaus, Lee Trevino, Masters champ Tom Watson and U.S. Open champ Hubert Green. Among them, they have won five British Opens and 17 other grand-slams titles so the prospects for a titillating final two days could scarecely be better.

For awhile today, as a faintly purplish haze again hung over the Firth of Clyde and the Ayrshire coast basked in another unScottish day of breezeless sunshine, it seemed as if the tame-when-becalmed 6,875-yard Ailsa course of the Turnberry Hotel would be ripped apart in a stampede of low scores.

Spaniard Angel Gallardo, the first man out at 7:30 a.m. equalled the longstanding British Open record of 65. Mark Hayes shattered that mark, set by heny Cotton in 1934 and matched eight times but never bettered since, with a 63, even though he bogeyed the par-four 18th.

Hayes took only 23 putts in his remarkable round.

Green, who had a lucky hole in one on the fourth hole, admitted that he had his eye on a 60 when he birdied five straight holes to go seven under for the day after 13 holes. Playing eight threesomes behind Hayes, he had the best scoring opportunities on the course still to come, but instead gave three strokes back to par on the final five and finished with 66, to go with his opening 72.

"I thought there'd be a lot more people under par today," said Watson who, like Nicklaus and Trevino followed his opening-day 68 with an even-par 70.

"That's a tribute to the golf course.It's not as casy as it looks. It was designed for wind and will never play easier then it did in the ideal weather conditions today."

Several players who failed to capitalize on the conditions early in the day were pleasantly surprised to find themselves still in the running at nightfall.

"I think I threw the tournament away today," said defending champion Johnny Miller, an early finisher, safter a 74. "The way I was playing. It's almost a sin to shoot 74. I was pathetic around the greens - I missed from eight feet on the first, from three feet on the third and three-putted five and six."

Miller expected his colleagues to shoot him out of realistic contention, but hiw two-day total of 143 is only six behind Foster, who was a stroke behind with 67 starting the day, also had second rounds of 74.

"I'm shocked that no one is six, seven or even eight under after two days of weather like we've had," said Trevino, the 1971-72 champion victory since the 1976 Colonial at Fort Worth, Tex.

Watson, who won at Carnoustie in 1975 when the wind and rain that are supposed to be an integra lpart of British Opens in Scotland also stayed away, played a rather lethargic round.

"I drove very well again, but my iron play was poor, and the putter didn't feel verygood in my hands," he said. "I felt tired. I woke up at 9 a.m., sat around all day waiting to tee off at 3:20, and was half asleep all day. I just found it very difficult to concentrate, for no particular reason."

Trevino, who downplayed his chances when he arrived here the day before the tournament ("I can't see myself winning, not in my wildest dreams . . . maybe if all the other guys get hit by lightning" I didn't have any trouble filling the time until his late tee-off.

"I slept until noon. That's an advangage of coming over here late - 4 o'clock here was 9 a.m. back home in El Paso. I was teeing off right after breadfast," joked Trevino, who still has a sense of humor and hopes to regain the form he had before back surgery last year. "I couldn't believe I slept 12 hours. Then I got up had some lunch and watched a little cricket on television.

"That was so exciting I almost fell back asleep."

Trevino, who had 12 one-putt greens Wednesday, took 33 putts today and chipped in a seven-iron shot from 35 feet for a birdie three on the 411-yard 13th, which is named "Tickly Tap." He holed a 15-footer on the 14th, but didn't make another putt longer than 2 1/2 feet.

"It was exactly the opposite of my round yesterday," said Trevino, who has also won two U.S. Open titles and one PGA. "Yesterday, I made everything on the greens and hit the ball terrible. Today I played better from tee to green than I ever hav ein any British Open, including the two I won, and putted just awful,"

Nicklaus, winner of the two British Opens (1956-70), three U. S. Opens, four PGAs, and five Masters, had similar problems. He hit the ball well, played smartly, but couldn't score one he got on the greens that are getting progressively slicker and faster. Pin placemetns today were not quite as demanding as on Wednesday, when they were all on slopes, but only Hayes had a superb putting round.

"I got off to a good start, made a couple of short putts, then played very well the rest of the way and made abolutely nothing," said Nicklaus, who was two under part after the seaside front nine. "The way I was hitting the ball, I could have scored very low."

Maltbie, 26, who won back-to-back tournaments as a rookie on the U.S tour in 1975, said it took him a few days to get used to driving on the first course he has ever played without trees. He has been distressed not to see links golf in the wind, but scrambled well and made some missing several in the three-to-five-foot range on the front line.

Hayes, 27, winner of the Tournament Players Division championship at Sawgrass this spring, eatled the 500-yard, par-fiva 17th with a drive, a three-iron, and a put that he routinely rolled in from 15 feet.

Using the cross-handed stroke he has just adopted. Hayes sank putts of 12, 13, 10 eight and 35 feet on his six birdie holes. The 18th, wher he left short chip out of the rough and over a mount in front of the gree, was his only bogey.

"I was missing on both sides with a conventional grip, so I expermented with the crosshanded sytle at the Western Open (in Chicago two weeks ago) and used it for my last round there," said Hayes, a British Open newcomer, who had an opening round 76 and is tied with Briton Peter Butler at 139, two stroke that about 15 golfers on the U.S. tour are now using.okes off the lead.

"Bruce Lietzke encouraged me. It's a very basic stroke that about 15 golfers on the U.S. tour are now using. The biggest thing is getting yourself to putt that way without being afraid people will laugh."

Green, after his bold string of birdies from the ninth through 13th, three-putted from 46 feet to bogey the 14th. three-putted the 16th. made three bad shots on the easily attackable 17th. and three-putted the 18th.

The halfway cutoff was 150 and 87 players in the field of 156 qualified for the third round Jim Seeley, the pro at Prince Georges Country Club in Landover, Md., shot 82.77 - 159 and missed the cut.