It was the Fourth Victory Rally since a revolutionary government slipped into power here while prime minister Eric Cairy was away, and the local politician at the microphone warmed the crowd with a rich island patois.

In 1973, he said, when the now-ruling opposition failed to upset Gairy's government, "Gairy said we caught him with his pants down."

"Tell me how we've caught him now," the politician grinned, and the crowd howled, knowing what was coming.

"NAKED AS A BUZZARD."

Since a coup last March 13 produced the first effective change in government this tiny former British colony has seen in 16 years, Gairy jokes-the similar and more profane the better-have become the hottest form of humor here.

The jokesters have an awesome range of material to choose from, including Gairy's longtime public fascination with outer space, and postcoup revelations that Mt. Royal, Gairy's palatial hilltop home, contained a secret "obeah," or voodoo room, complete with ritual donkey's eyes, saltpeter and dusty red robes.

But once the exuberance-much of it sheer excitement at any change in this isolated spot-dies down, Grenadians and their new government will have to decide how much revolution they want, or are capable of.

The organizers of the English-speaking Caribbean's first coup are tall, dark and serious young men. Many were educated abroad, but still tend to end conversations with the local "all right, cool," sign-off.

Their ideology is leftist, to varying degrees. Prime Minister Maurice Bishop, the 34-year-old British-trained attorney who was cofounder of the New Jewel Movement opposition to Gairy in 1973, is generally considered a soft-line socialist.

Those who have made such distinctions believe Finance Minister Bernard Coard, a political science and economics graduate of Brandeis University with a master's degree in political economy from Britain, is the hard-line Marxist of the 14-member revolutionary government.

While revolutionary rhetoric is rampant, and cheered by at least the youthful portion of the population, their actions so far have been inconclusive.

The local radio station, renamed Radio Free Grenada, the Voice of the Revolution, still fills its broadcasts primarily with U.S. gospel programs and lengthy song dedications to "mummy and dad."

The new People's Revolutionary Army huffs and puffs through the steep, winding streets of St. George's population approximately 6,000, each morning, jogging into shape to combat a feared countercoup that would be launched by Gairy from his current residence in San Diego, Calif. But there is little evidence of heavy security on most of the island.

The government has publicly thanked Cuba for unspecified help and has made no comment about a shipment of mysterious crates unloaded at St. George's from a Cuban ship two weeks ago. But the subject has been vigorously discussed in the privately owned island newspaper, which demanded to know if the crates contain arms.

The revolutionary government has suspended the island constitution and replaced it with a series of "people's laws." One of the first laws noted that, unless specified, previous laws remained in force. The rest have dealt primarily with things like price-freezing to avoid profiteering.

On the surface, little has changed here. Reggae music still pours from the tiny crackerbox houses perched along narrow, potholed roads through the volcanic jungle. While government officials occasionally call each other "comrade," most of Grenada's 100,000 people still greet each other in formal, colonial English flavored with broad smiles.

Tourists, seeking the peace and quiet that this 133-square-mile hideout is known for still trickle into the island's 800 hotel and guest house rooms where, as usal, tap water runs only sporadically and the supply of soda popa frequently runs out.

Although the government still holds approximately 60 members of the previous government in jail, many have been gradually released. At last week's victory rally, Bishop reminded the crowd that those who did not want to accept supporters of the Gairy government back into daily life had a "wrong attitude" and an "incorrect position."

"We must welcome all sisters and brothers" in the building of a "new society," he told them.

Whether the new government has the materials to build a "new society," of whatever ideological bent, remains questionable.

While Bishop has exhorted everyone to "work haed and study hard," he warns that "the answer cannot be magic." Still, he and other officials have promised Grenadians-the majority of whom work in the tiny banana, nutmeg and cocoa plantations that support the island's fragile economy-pension and social security programs, a solution to 50 percent unemployment, and a restored national treasury.

The answer to where and how Grenada's political and economic revolution proceeds will likely determine how much the Caribbean region, and the bigger world powers, will help or hinder it.

So far, the United States has provided lukewarm acceptance of the new government and offers to help vitalize the economy. Its enthusiasm is dampened by the revolution's rhetoric and obvious Cuban interest.

In the rest of the Caribbean, reaction to what has happened in Grenada ranges from strong official support, in Jamaica and Guyana, to unspoken disapproval, in Trinidad and Tobago.

Others basically support the new government out of a deep dislike of Gairy, but remain uncomfortable over the precedent set by the coup and anxious for a promised free election. CAPTION: Map, no caption, By Richard Furno-The Washington Post