The merchants of marathoning own this city today, hawking T-shirts, jogbras, bee pollen and even record albums ("Daydreams of a Night Jogger" is the hot number) to the lean and leggy legion of athletes gathered for the 83rd Boston Marathon.

The runners, praise be, will take over the town Monday, when 7,800 official entrants - and an expected 3,000 or so cheeky crashers - line up in sleepy Hopkinton, Mass., to begin pounding the pavement toward the Prudential Building, so far away in downtown, bustling Boston.

The race will begin promptly at noon, and just about 130 minutes later the first man will cross the finish line having whooshed at a 5-minute-a-mile pace through a 26-mile, 385-yard funnel of humanity lining the route.

The favorite of the crowds - and this year, for the first time, Las Vegas, too - is Bill Rodgers of nearby Melrose. He is a two-time winner, the defending champion and American record holder in the marathon with a clocking of 2 hours 8 minutes 55 seconds, set in Boston in 1975.

The Nevada nabobs are accepting marathon wagers this year and Rodgers is a 2-to-1 favorite.

Rodgers trains on the Boston course and his running store is along the route, at the 22-mile mark. By the time he reaches that point, Rodgers is expected to be leading, although he admits "this is the strongest Boston field ever."

There will be 10 sub-2:12 marathon men in the field, though two of last year's top five Boston finishers, second-place Jeff Wells (a sore Achilles) and fourth-man Jack Fultz (torn tendon), will not race.

Fultz is a 1976 graduate of Georgetown who won Boston that year. He and Rodgers are good friends and occasionally train together. Today Fultz said, "There's no question he will be the man to beat.

"Bill is healthy and I know he's feeling confident about the race. He's also running this to prove a point more than anything else. He finished sixth at Fukuoka (Japan last December) and if he loses here, I think people will come down hard on him. And he knows it.

"I believe he feels he has to win. If he does, everything will be fine. If he loses, it could be devastating to him.

"But Bill also has a great advantage here just because of his reputation. Once you get yourself on top like he has, other runners have a tendency to be intimidated by you when the going gets tough. You may be able to keep up with Rodgers, but you keep asking yourself, 'I wonder how much I've got left?'

"When you run against Rodgers, you know what he's got left and that can destroy a lot of people who might be able to beat him physically, but not mentally. There's a big mind game going on out there, and that's always in Rodger's favor."

So, too, is the weather. The forecast for Monday calls for temperatures in the high 40s, with overcast skies and light breezes - perfect conditions for a marathon. Rodgers always has preferred nippy weather, and no doubt will wear the white gloves that have become his trademark.

Japan's Toshihiko Seko won on his home course at Fukuoka last December and will run Monday. Seko, 23, says he will try to stay with Rodgers and attempt to pick up the pace on the Newton hills, 17 miles into the race.

That is precisely where Rodgers, a superb downhill runner, took command a year ago - on the downside of the famous Heartbreak Hill. At that point, the runners get their first look at the distant Prudential Buildingg, and the crowds press so close there is hardly room to pass.

Other quality contenders include Finland's Esa Tikkanen (third last year), Randy Thomas of Boston (fifth in 1978), Kevin Ryan of New Zealand (sixth), and Englishmen Trevor Wright and Crhis Stewart.

Six South African runners have been banned in Boston by the AAU, but they will run unofficially.

Bruce Robinson of Silver Spring, Md., heads a large contingent of Washington-area runners. Robinson, who owns a sporting goods stor in Bethesda, finish 23rd last year in 2:18.

The women's field has doubled from a year ago to 520 official entrants. Gayle Barron, last years' women's champion, will run wired for sound. A four-pound transmitter will allow her to broadcast the race as a participant for a local television station.

That extra weight probably will not allow her to repeat. The top contenders include Patti Lyons of nearby Quincy, the Hawaii marathon champion; Penny DeMoss of Los Altos, Calif., second to Barron a year ago, and Kim Meritt of Racine, Wis., the 1976 Boston winner.

Behind the leading runners will be a field that includes 20 wheelchair athletes, at least one blind runner and thousands of others who have completed at least one marathon in 3 1/2 hours or less.

Today, they were consumers buying souvenirs of the most famous marathon in the world.

Tomorrow, they become consumed with the notion of finishing it. Quickly.