The Boston Marathon has 85 years of tradition. New York has 26.2 miles of the world's most enthusiastic spectators lining its run. Washington can't compete in either of those categories. But it does have monuments, Marines and Mack Schwab.

"I'm about as slow as they come," says Schwab, at 73 the oldest of the 11,000 runners expected to compete in Sunday's Marine Corps Marathon. "If there's anybody running behind me, I'll be surprised."

Sunday at 9 a.m., one blast from a 105-mm cannon FOCUS beside the Iwo Jima Memorial will start a 26-mile, 385-yard race through Northern Virginia and downtown Washington. No world records appear to be in danger.

"This is truly a Peoples' Run," says Marine Lt. General Richard E. Carey, commander in chief of this seventh annual marathon that has attracted participants from 50 states and 27 countries. "We want to keep it so that anybody can run."

There will be some prominent people running in the race, including Secretary of Agriculture John Block, Idaho Sen. Steve Symms and former astronaut Michael Collins.

Laura DeWald, a 25-year-old graduate of Washington and Lee High School in Arlington, is the favorite among the women. DeWald, who quit her job this summer to train full time, has run a 2 hour 34 minute marathon. The Marine Marathon record for women, set by Jan Yerkes of Pennsylvania in 1980, is 2:41.48.

Yerkes is not competing this year, but Cynthia Lorenzoni of Charlottesville, who won last year's race in 2:50, will be back to defend her title in the world's second-largest marathon (New York is first).

"I feel like I can really go out there and tear up the course," says DeWald. But others wonder if she has recovered fully from the New York Marathon two weeks ago.

The top-seeded male runners include Shawn Welch of Arizona, England's Mike Hurd of the Royal Air Force and Carl Hatfield of Morgantown, W.Va., a two-time winner of Washington's 10-mile Cherry Blossom Run. They will be trying to break the course record of 2:16.30 set last year by Dean Mathews of Georgia. Mathews ran in New York two weeks ago and will not compete.

Even if most of the country's top marathoners had not competed in New York last month, it is unlikely many would have run here. While some marathons give under-the-table expense money to the top finishers, the Marines have refused to give away anything more than trophies, T-shirts and oranges. "If we go commercial it will spoil the whole flavor of it," said Carey earlier this week.

If the elite runners have shunned the race, there has been no shortage of foot soldiers willing to pay $10 to enter. As of yesterday, there were 10,500 runners registered. Race officials expect 11,000 to be at the starting line.

If past years are any indication, there will be a shortage of spectators Sunday. While more than two million people lined the streets of New York last month to watch a marathon that was carried live on television, officials here will be happy with 50,000 watching.

"The problem is that the part of Washington where the race is run really isn't residential," said one Marine officer. "To watch it people have to commute there. They have to be marathon enthusiasts already."

Two years ago the race, which started with 1,200 in 1976, was marred when it was discovered the course was one-third of a mile short of the required distance. "The problems have been ironed out," says Carey.

Some interesting people to watch will be Ken Archer, a 33-year-old from Bowie who will compete in a wheelchair, and 8-year-old Chuckie Eisele of New Jersey, who holds five national running records for his age group.

There will be five wheelchair racers trying to break the course record of 2:26. Archer, a Labor Department mathematician, completed a marathon in Richmond two weeks ago in 2:22 over a course that was much worse than Washington's.

This will be Eisele's second marathon. The third grader, who is already endorsing Adidas running gear, hopes to break the national age-group record of 3:54.34 set in 1972.

Schwab, a retired television producer now living in Columbia, Md., says he is only interested in finishing the run before the traffic is again let loose on the course.

Asked why he runs marathons, Schwab, who began running on the advice of his doctor, is hard pressed to explain. "About four or five months before a marathon, you get the literature and find yourself signing up. Then you tell everybody. It gets to be an obligation."

But one thing he is sure of, he's not out to beat anything but bad health.

"About the only thing I get medals for now is living long. That's fine with me," he says.