The Honolulu Marathon, which will be run for the 41st year on Sunday, is on pace to bolster the state’s $15 billion visitor industry during the seasonal lull right before the winter holidays.

While entries for this year’s race were flat going into the Honolulu Marathon Expo, organizers say that this year could still pull ahead of 2012. Before the opening of late registration on Wednesday, 29,575 runners had entered the race compared with 29,937 at the same point last year. Another 2,000 to 4,000 runners are expected to enter before Saturday’s 5 p.m. cutoff, topping last year’s total of 31,083 racers.

(Marathon entries at the end of Wednesday, after one day of late registration, were up to 29,786.)

Even if the upcoming race does not break last year’s record, the economic impact of the event remains significant, said Jerome Agrusa, chairman of Hawaii Pacific University’s Travel Industry Management program, who supervises an economic impact study on the marathon.

"Over the last eight years, the Honolulu Marathon has generated more than $100 million in annual sales," Agrusa said.

Last year’s event pumped a record $132.8 million in sales into Hawaii’s economy. It boasted the best economic impact since 2007, when the race generated $108.9 million. Agrusa expects that this year’s race will be economically comparable.

For starters, the race continues to be a significant tourism draw. Altogether, about 18,039 people from 45 countries had pre-registered for Sunday’s event. Because most visitors bring at least one person, Agrusa said, marathon-related visitors could top 36,000.

Takeshi Sakai of Hankyu Travel International Co. Ltd. said the company brought 350 runners for the race and that most will bring friends and family, stay multiple days and participate in a variety of activities.

"It’s our most popular marathon because the weather is good and the race doesn’t limit participants or force them to finish on a strict time," Sakai said.

As of Wednesday evening, 13,088 marathon entrants had signed up from Japan. By an earlier count, 2,064 mainlanders and 861 people from foreign countries other than Japan also were expected to run.

Rodney Whitaker and his 12-year-old son Logan are among the travelers from the mainland.

"We like it because it’s novice-friendly," said Whitaker, of Vancouver, Wash. "The first time Iran the Honolulu Marathon, I got beat by a 78-year-old woman with a broken leg."

Hawaii’s allure helped Whitaker overcome his initial humiliation to return four more times.

"Running this marathon was first on my bucket list and running it with my son was second," he said. "This is paradise. My wife, Kersten, is going to join us tomorrow. We’ll stay for eight days."

Young Logan also plans to enjoy water sports and visit restaurants like The Shorebird and Cheeseburger in Paradise. But he’s especially looking forward to scarfing down race-day malasadas.

"I’ve had them before, but they taste five times better after you cross the finish line," he said.

Meanwhile, Kelly Sanders, area managing director of Starwood Waikiki, is savoring the extra business that the well-timed race has brought, especially in the form of group bookings at the Sheraton Waikiki and the Sheraton Princess Kaiulani.

"It’s filled rooms during what is generally a soft period," Sanders said.

Barry Wallace, executive vice president of hospitality services for Outrigger Enterprises, said he thinks this year’s marathon business is softer than last year’s. But even so, it’s made a noticeable difference in Waikiki business.

"Bookings for the event are about 15 percent below last year," Wallace said. "However, several of our properties, including the Outrigger Reef, the official marathon hotel, have seen a 10-point occupancy jump."

The event also has pushed business to off-beach properties, he said.

"Many of the marathon guests don’t care about an ocean view. They are here to train so they book off-beach properties," Wallace said.

Still, according to research by HPU’s Agrusa, marathon guests typically spend more than other leisure visitors.

"Japanese runners spend about $351 per day," Agrusa said. In comparison, daily spending for all Japanese visitors through October averaged $308.

A stronger U.S. dollar means that Japanese runners have less buying power this year, but Agrusa said he does not expect major spending differences.

"They are becoming more like us. When we travel, we spend what we need or use credit cards to have a successful race and to enjoy our vacation,"Agrusa said. "Only afterwards do we realize that we spent too much."

Shopping was on the agenda Wednesday for returning marathoner Chihiro Takahashi and her mother, Hisae Takahashi, who came for the race-day walk.

"We enjoy the atmosphere here and all of the shopping, shopping, shopping," said Chihiro Takahashi, who was perusing local goods at the Ben’s Craft stand during the Honolulu Marathon Expo at the Hawai’i Convention Center.

Arnold Policarpio, son-in-law of the owner of Ben’s Craft Inc., said the marathon typically boosts pre-holiday sales 20 percent.

"We are always waiting for the marathon. We think it’s a big help to local companies," Policarpio said. "The Japanese are typically our biggest customers. They buy Hawaiian everything."

There also is a good chance that racers from Australia and New Zealand, who are enjoying a particularly favorable exchange rate, will join this year’s big spenders, Agrusa said. "Their currency is the highest that it’s been in years," he said.

Kent Yoshioka, a first-time exhibitor at the Honolulu Marathon Expo, said the traffic will improve business for his firm, LEDSystems Hawaii. "We just opened in February so we need exposure and product awareness," said Yoshioka, whose bright HALO-brand LED belts and pet collars attracted a crowd Wednesday. "This seemed like a good way for us to market to a target audience of visitors and locals."

The event and others like it also support Hawaii Tourism Authority’s efforts to showcase the state, said Mike Story, the HTA’s tourism brand and sports manager.

"Sports tourism is a billion-dollar industry. It’s a great way to leverage your destination, especially during softer seasons,"Story said. "When televised, the exposure can be worth millions."

The marathon annually spends $750,000 for a nationally shown one-hour TV special that promotes the race and Hawaii.

"These kinds of shows highlight the fact that Hawaii has world-class natural resources to make world-class events for the world’s best athletes," Story said.

Sporting events like the marathon also introduce first-time visitors to the isles and give repeat visitors an excuse to return, he said.

To be sure, Jerold Chun, a local boy turned California-based molecular neuroscientist, will hit the race route for the 41st time. "I’m the last of the family to continue," said Chun, who was just 13 when he ran his first Honolulu Marathon in 1973. "This is a fantastic marathon. I’ve managed by hook or by crook to get back each year."