Leading Maryland congressmen, stymied for 14 years in their attempts to get federal funding to deepen the port of Baltimore, reaffirmed their commitment today to make harbor dredging a top legislative priority when the 99th Congress convenes in January.

In October, Congress approved a water projects bill that contained federal funds for port dredging, but President Reagan, who earlier had endorsed the $350 million Baltimore harbor project, vetoed the measure.

At a hearing here today, local and state politicians, labor and business leaders, and representatives of the port community told the congressmen that Maryland's economy will stagnate if larger ships are not able to dock in Baltimore.

"The port has entered a new era, and the traditional rules no longer apply," said Eamonn McGeady, president of the Greater Baltimore Committee's transportation council. "There are some dark clouds on the horizon . . . . If we do not act decisively we could become a backwater facility."

Business leaders estimate that the port generates roughly $1.2 billion for harbor industries and an additional $1 billion in personal income annually for Maryland residents. About 79,000 jobs in Maryland are related to port activities.

"The people we have to sell are David Stockman director of the federal Office of Management and Budget and the administration," said Rep. Steny Hoyer, a Prince George's County Democrat. "Everyone else is for port dredging."

Maryland's eight members of the House of Representatives and two senators support harbor dredging.

Maryland Transportation Secretary William K. Hellman told the six congressmen at today's hearing that the state would continue to consider sharing some cost of the dredging project. But Hellman said the federal government must agree to pay at least 50 percent and to reimburse the state for the cost of constructing the disposal sites at Hart and Miller islands at the edge of the port.

Baltimore for many years has been one of the East Coast's premier seaports, with a 42-foot channel that serves as a trade route for coal, chemicals, minerals and container cargo. But in the last decade, the shipping industry has turned to larger ships to haul heavier loads, and as a result Baltimore's status as an elite world-class port has diminished.

Maryland politicians and business leaders agree that to regain its edge in the face of aggressive competition, Baltimore must deepen its channel to at least 50 feet so that it can accommodate supercolliers -- 100,000- to 150,00-pound ships that carry coal and other cargo -- and operate at capacity.

"I went down to Charleston, S.C., and watched the boats go by -- like automobile traffic," said Baltimore Mayor William D. Schaefer. "If we don't get the dredging done, no ships will come up here."

The Maryland delegation's legislative attempts to get federal funds for the harbor have been an exercise in political frustration. When harbor dredging was first proposed in 1970, opposition came largely from environmentalists who were concerned about the impact of dumping silt on the Hart and Miller islands. Environmental groups found an ally in Rep. Clarence D. Long, a Baltimore County Democrat and member of the Appropriations Committee who repeatedly blocked funds for dredging.

Long, who was defeated in November, reversed his position on dredging in 1981, but a declining export market, deregulation of the shipping and rail industries and the Reagan administration's cuts in federal spending had emerged by then as equally formidable hurdles for proponents of the harbor project.