At 1 o'clock this afternoon, the D.C. Armory will figuratively lower its gangplank, hoist its most dashing flags and shout, "Welcome aboard" to the thousands who make attendance at the Washington International Boat Show an annual rite.

As in years past, 180,000 square feet of display space will be jammed with more than 500 cruisers, skiboats, runabouts, houseboats, fishing boats, sailboats, canoes and dinghies. And alongside will be gobs of motors, hardware, accessories and nautical miscellany.

This year, the "queen" is probably the largest sailboat displayed in the show's 17-year history. The craft is a Gulfstar 50-foot auxilliary cruiser that boasts a Bimini top an dodger should there be too much sun and spray, an unusual furling arrangement should there be too much wind (the mainsail rolls right inside the mast) and a 62-horsepower Perkins diesel engine should there be no wind at all.

Below, the six-person crew can enjoy three staterooms, a sumptuous galley, conditioned air, music wherever they want it and plenty of expensive teak. It all adds up to a most inpressive boat and a most impressive price tag: $150,000.

Alongside the queen will be another Gulfstar that's even more costly. It's a 44'foot motor cruiser that is perhaps the largest and most expensive power boat ever displayed at an indoor show. It uses twin 160-horsepower turbo-charged Perkins diesels to attain at 14-knot cruising speed and it has 500-gallon fuel tanks so it can cross oceans.

Like the sailboat, it sleeps six in three staterooms and is just as plush. It also has a few extras that couldn't fit into the sailboat: a trash compactor, a washer/drier, a wet bar under a covered afterdeck and some beautiful furniture. Add to all that a radar and an autopilot adn you've got a boat that costs $165,000.

Of course, not every boat in the show is ultraexpensive. Many cost about what would pay for an automobile. And at least one will cost nothing. A 12-foot Mayflower will be the prize in a free drawing. The unsinkable craft is worth $800 and can do duty as a sailboat, a rowboat and, with a small outboard, a fishing boat. The drawing will be held Sunday, Feb. 26, the shows final day. The winner need not be present.

Show hours are 1 p.m. to 10 p.m. today through Monday: 5 p.m. to 10 p.m. Tuesday through Friday; 1 p.m. to 10 p.m. Saturday, Feb. 25, and 1 p.m. to 8 p.m. Sunday, Feb. 26.