The Chesapeake Challenge offshore powerboat racing series returns to Baltimore tomorrow and Sunday, and race officials said yesterday that they expect thousands of spectators and thunderous competition.

"There are only 10 of these events in the nation, and we are one of them," said John Wilmoth, race chairman for the Chesapeake Bay Power Boat Association. "Last year was big, and this year will be even bigger."

Wilmoth said perhaps as many as 80 boats will compete on the Patapsco River in 11 national pro classes and the Amateur Open competition for area racers. The pros race for $30,000 in prizes.

The Chesapeake Challenge is the midway point in the American Power Boat Association's National Offshore Series, and race organizers expect close competition after an abbreviated race series in Sarasota, Fla., over the July 4 weekend.

"We're expecting a strong field, especially after what happened in Sarasota," said Wilmoth. "There was lightning on the course down there, so they cut the race short, and that fouled up a lot of people in the standings.

"We expect a lot of boats to use this event as a makeup race -- including some of the West Coast teams, which ordinarily might not travel this far."

Race organizers won't have a complete count of boats per class until entries close at 6 a.m. today.

But as of yesterday afternoon, world champion Drambuie On Ice was the only USA-1 class racer on site at the Baltimore Marine Center on Boston Street.

Alcone Motorsports, the closest challenger in USA-1 (39- to 48-foot, 2,000 horsepower catamarans), will not race here because driver Matt Alcone is competing in Europe. There are, however, about 10 other top-class boats that are pre-registered for the event and could arrive before the entry deadline.

In the Super Vee class (39- to 43-foot, 2,200 horsepower monohulls), only 30 points separate the top three boats in the standings. Citgo Supergard, CGS Fercious and Nemschoff, the Nos. 1, 4 and 5 boats, arrived yesterday.

"We'll be getting boats in here all night and throughout [today]," said Carol Boswell, one of more than 50 CBPBA volunteers working the Challenge.

Hooters, Citre Shine and Tivoli, the top boats in Pro Stock, Stock and Offshore B, were trucked in yesterday, and each drew small gatherings of spectators as transport crews cleaned the boats and set up work areas for the weekend.

But while the seven national classes often draw much of the attention from race fans, the Factory 2 class is stealing some of the thunder from the high-tech, high-horsepower racers.

In Factory 2, racers use identical pairs of 500-horsepower Mercruiser motors in vee hulls ranging from 30 to 39 feet. At Sarasota, 18 boats crossed the starting line. In Corpus Christi, Texas, a few weeks earlier, five F-2 boats crossed the finish line within 30 seconds of each other, and nine boats were separated by less than a minute.

"The big attraction for me is that it's no longer checkbook racing," said Bob Eubanks, an industrial waste recycler in Mogadore, Ohio, who is the throttleman aboard his 38-footer, Twisted Styx. "I'm a working man, and this is something I can enjoy and afford."

While Drambuie On Ice spends well over $1 million a year on its racing campaign and travels with set-up crews and mechanics in two tractor trailers, a van and mopeds, Eubanks has a scaled down operation.

"I've got about $230,000 in what you see here, from spare tires to paint jobs," said Eubanks, waving toward boat, trailer and tow vehicle painted in identical color schemes. "I don't carry a spare engine to most events. I can handle the mechanical work, and I drive the truck."

The Factory 2 class was formed two years ago to foster increased grass-roots interest in offshore racing. APBA official Carrie Rasmussen said the growth in that class has been better than expected -- particularly because of racers like Eubanks.

"When I started I was driving a 38-foot Scarab pleasure boat that fit right into this class," said Eubanks. "We just threw the helmets on and went out and had fun.

"That was in a boat right off the showroom floor, and we raced that first season with the refrigerator and all the cruising gear still in it -- which, of course, brought on a lot of jokes about whether we were running the blender to make crushed ice drinks while we were racing."

Joking aside, Eubanks said, from a practical standpoint, the stock motors in the Factory 2 class should run all season without major breakdowns, and cannot be altered after they are sealed at the factory.

"And if anyone so much as rejets a carburetor or advances the timing, they are disqualified," said Eubanks. "It has become a race of hulls and drivers rather than high-tech engines and mechanics."

Wilmoth said crowds at the marine center, where race headquarters and shoreside activities are centered, and the number of spectator boats around the course on the Patapsco River are expected to be larger than last year.

"We had about 5,000 people on shore and some 3,000 spectator boats last year," Wilmoth said. "We expect more people on shore this year because it is free."

If slip reservations are any indication of potential size of the spectator fleet, the marine center said it has put aside almost twice as many spaces for race weekend boats as last year.

If you're going

What: Chesapeake Challenge Offshore Powerboat Race and Festival. Call: 410-675-8888.

Where: Shoreside activities will be based at the Baltimore Marine Center at Lighthouse Point on Boston Street.

When: Racing days are tomorrow and Sunday, with racing scheduled to begin at 1 p.m. each day on the Patapsco River over a 9-mile loop extending from Lazaretto Point beyond Fort Carroll.

Admission: Admission to grounds at Baltimore Marine Center is free. Wet pit passes cost $3 a day or $5 for both days.

On-water spectator areas: Three anchorage areas have been set by the Coast Guard on the south side of the race course. Shoreside spectators: Two big-screen TVs at Baltimore Marine Center or from Fort Armistead Park.

Public parking: Free at lots at First Mariner Bank on Clinton Street and North Shore Anchorage at Aliceanna and Boston streets.

Schedule of events

Today 9 a.m. to 6 p.m. -- Race registration for national and NCCT classes, Baltimore Marine Center. 11 a.m. to 11 p.m. -- Concession stands open, Baltimore Marine Center.

Noon to 2 p.m. -- Blessing of the fleet at the Inner Harbor promenade.

Tomorrow 11 a.m. -- Concession stands open and sweep boats depart. 1 p.m. -- Club racing starts. 2 p.m. -- APBA class racing starts. 7 to 11 p.m. -- Awards ceremony at Baltimore Marine Center.

Sunday 11 a.m. -- Concession stands open. 11: 30 a.m. -- Sweep boats depart. 1 p.m. -- APBA class racing starts. 4 p.m. -- Awards ceremony.