Page Groton, assistant to the president of the Boilermakers' Union, was so upset that his voice shook as he shouted at Navy Secretary John F. Lehman Jr.

"You say you're going to build up the Navy to 600 ships, but how many more are going to be foreign junk that you buy out of foreign fleets while we get s--- for work?" he demanded.

Not only did the Navy buy two used freighters out of Britain's mothball fleet, but also "the Military Sealift Command has contracted with a South Korean yard to overhaul a Navy tanker over there for $656,000," Groton said.

His tirade completed, Groton sat down to the applause of about 150 delegates to the annual shipbuilding conference of the AFL-CIO's metal trades department at the Shoreham Hotel. Lehman, who had ventured into the lion's den to defend the Reagan administration's shipbuilding programs, smiled sheepishly and responded, "What can I say?"

In fact, such contract awards to foreign yards by the Navy are routine, and the dollar amount is relatively small. But the strong words from Groton were indicative of the sentiment among the union officials, who made no secret of their feelings of betrayal by the administration.

Reagan pledged in the 1980 campaign "that he would work to preserve the shipbuilding industry and its essential nucleus of skilled workers," said Paul J. Burnsky, president of the metal trades department. "Today we face disaster."

Lehman said the administration's commitment to build up the Navy from 480 ships today to 600 by 1989 would create at least 75,000 new jobs in the shipyards. He said the shipyards already have contracts to build or refit 106 ships, "more than at any time since the height of the Korean war," and that the defense buildup has been "good for the economy and good for employment."

But it wasn't the Navy program that was the focus of the union leaders' anger. It was the administration's economic incentives to the operators of American-registered merchant ships to acquire their new vessels in lower-cost foreign shipyards.

The "build abroad" program, which permits American merchant ship operators to retain their federal operating subsidies while building or rebuilding their ships in foreign yards, is a key part of the administration's maritime program, in which subsidies for domestic construction have been scrapped. The House has refused to accept a Senate-approved extension of the build-abroad program, and the issue will have to be settled in the upcoming lame-duck session.

Employment in private shipyards was 141,000 when Reagan was inaugurated, dropped to 124,000 in July, 1982, and still is going down.

James Kennedy, an AFL-CIO official, ridiculed the notion that U.S. workers displaced from jobs will find new work in service industries. "The idea that we can live by cutting each other's hair and shining each other's shoes is radical nonsense," he said.