MUIRFIELD, SCOTLAND, JULY 16 -- There is no golf tournament in the world quite like the British Open. At no other championship -- major or minor -- can the character of the golf course change so swiftly. Nowhere else is the field so diverse and full of characters. Nowhere is the game less predictable.

Day one of the 116th Open Championship today at Muirfield was a typical British Open day if there ever was one.

The leader after 18 holes is Rodger Davis, a 36-year-old Australian who is playing golf today because a motel deal went sour on him four years ago. Davis shot a course-record, 7-under-par 64, playing in the morning when the winds were light, the sun was out and the scores were low.

His closest pursuers, all three shots back at 67, are Lee Trevino, 47, the two-time champion; Bob Tway, the PGA champion, and Ken Green, the former Masters one-day wonder who said today that he had fired his sister as his caddie "because she was becoming more famous than me."

Several players slightly more famous lurked just behind the top four. Masters champion Larry Mize, PGA leading money winner Paul Azinger and Nick Price, who almost won this tournament in 1983, were at 68. Tom Watson, Bernhard Langer, David Graham and Craig Stadler -- in spite of a rules slip-up -- were at 69. Defending champion Greg Norman was at par 71 after double-bogeying 18 and Seve Ballesteros was at 73 after breaking a string of 17 pars with a double-bogey at 18. Jack Nicklaus was one shot back at 74 and Arnold Palmer, playing here for the first time since 1984, shot 75, the same score as U.S. Open champion Scott Simpson, who began with a double-bogey.

Of the top four, only Green played in the afternoon. This was a day that started with players in shirtsleeves and ended with a spectacular sunset. In between a steady rain swept in off the Firth of Forth, turning the tame course tough.

"We had it great," Trevino said after his morning round. "Going out, we were downwind and then the wind turned around and we were downwind coming in. . . . That's luck."

The afternoon players weren't nearly as lucky. Some, like Watson, shrugged off the rain and the wind. "It wasn't that bad at all," he said. "No question, in the morning the conditions made it almost like American-style golf. We {in the afternoon} had the wind as a definite factor. But it wasn't that bad."

Others, like Norman, were less than thrilled. "I'm just glad not to have a round in the mid-70s," he said. "We played almost all the long holes into the wind. You're talking the difference between a 1- or 2-iron or middle irons on those holes. It makes a lot of difference when you play."

That is as much a part of this tournament as the knee-high heather that traps wayward golf balls and the hard greens.

The players who win here are those who not only understand the foibles of links golf but accept them. Among today's leaders, Trevino is the only one who has proven he can win in these conditions, although Davis did lead briefly on the final day in 1979 before finishing fifth.

Three years later, Davis quit golf, put his money into a motel venture on the coast in Queensland and retired so he could be with his family.

"The motel deal didn't work out too well," Davis said today. "I was sort of forced back onto the golf tour. I really didn't want to travel that much anymore. My daughters {age 16 and 12} miss me when I'm away and I miss them. But I had to make a living."

In the last year, Davis has made a very good living -- earning about $500,000 playing all over the world. He won five tournaments on the European Tour last year, but didn't rate an invitation to this year's Masters.

Today, Davis birdied Nos. 2 and 3, knocked a sand wedge to within three feet for another birdie at the fifth, had a two-putt birdie at the sixth (a hole that couldn't be reached in two in the afternoon) and then chipped to within three feet for his fifth birdie at the ninth. That got him out in 31.

"Then I made my only mistake of the round at the 10th," he said. "I had planned to hit a 1-iron off the tee before the round but I was 5 under and feeling good, so I hit driver. I paid for it."

He knocked the driver into the right fairway bunker and was happy to escape with a bogey. "The winner of this tournament will not be the guy who keeps it in the fairway," Davis said. "He'll be the guy who keeps it out of the fairway traps."

Davis kept it in the fairway the rest of the way and on the last five, three putts just stayed out of the hole.

Davis has become a solid player since going back on tour in late 1983. When he decided to come out of retirement two longtime friends, both rugby players, took him aside and told him he would play much better if he rid himself of his well-earned beer belly. Under their guidance, Davis went on a serious conditioning program and although he still likes a beer, he is now a slender 5 feet 10, 172 pounds and cuts a natty figure on the course wearing the plus-twos that he began wearing long before Payne Stewart made plus-fours fashionable.

Davis says he isn't certain what he will do after this season: take his family to the United States full-time or semi-retire to Australia. "I would say winning here might convince me to keep playing the game," he said with a laugh.

One of his playing partners, Stadler, was not nearly so jolly. Two years ago, Stadler missed the cut at Royal St. George's because he was sick. Last year, he damaged tendons in his hand at Turnberry and didn't finish the first round. Today, he walked off the course thinking he had shot 67 only to learn it was a 69.

"Someday," Stadler said, "I'm gonna learn all these rules." In February, Stadler was disqualified in San Diego after using a towel so he could kneel under a tree to hit a shot. A TV viewer in Iowa called to tell officials Stadler had broken a rule. The officials agreed and Stadler -- who already had signed his card -- was disqualified for posting a wrong score.

Today, he learned of his error before he signed his card. The problem came at the fifth hole. Stadler drove way right -- "only fairway I missed," he said -- and found his ball imbedded. Thinking he had a free lift, Stadler called Ian Woosnam, the third man in the group over. Woosnam agreed the ball was imbedded and that Stadler could take a drop. He did and proceeded to make a birdie 4.

"Then, after I got in one of the recorders told me that some fan told him what I did," Stadler said. "Apparently it's a rule here that you can only take a lift on an imbedded ball in the fairway. I didn't know."

The penalty was two strokes. Stadler said he would have lifted the ball and taken a one shot penalty if he had known the rule so he only lost one shot. "I wasn't thrilled when they told me," he said. "But it's still better than last year. At least I'm not going home."

Green has no past British Open experience to compare this one to. But he certainly was relaxed, "until I got to 18 and calmly proceeded to choke," he said. He was 5 under by then, helped along by an eagle on the 550-yard, par-3 17th hole when he sank a wedge shot from about 70 yards, and his bogey still left him at 67.

"I hit one really bad drive," he said. "That was at 11 where I hit the ball so far right it went into one of the bars. I would have made par but they didn't have any tequila."

Rummells Out Front

Associated Press

COAL VALLEY, Ill., July 16 -- David Rummells, a native of nearby West Branch, Iowa, shot a 7-under-par 63 today for a one-stroke lead over Mark McCumber and Brad Fabel after the first round of the $500,000 Hardee's Golf Classic.

Teeing off in the day's first threesome, Rummells, who had never led any round in more than two years on the PGA Tour, had six birdies on the front nine and two on the back nine of the 6,602-yard Oakwood Country Club course.

"I wanted to put on a good show for everybody," said Rummells, who was playing before about 30 hometown folks.

His score was one stroke off the record in the tournament, formerly the Quad Cities Open.

"The winds made it difficult today, but the greens were in beautiful condition," said McCumber, who won last week's PGA event at Kingsmill in Williamsburg. Three Tied at 5 Under

United Press International

DANVERS, Mass., July 16 -- Sally Quinlan shot a 5-under-par 67 to share the lead of the $300,000 Boston Five Classic with Amy Alcott and Cathy Marino.

Jan Stephenson, recovering from broken ribs suffered in a May car accident, and Donna White were one shot back.

Jody Rosenthal, winner of last week's Du Maurier Classic, shot a 69.