The revolt by some members of the Marine Engineers Beneficial Association against leaders they have called unresponsive and greedy is the first step on the road to a single American seafarers' union, said a key maritime labor leader.

"You have started a building block to one licensed (ship officers) union down the line," said Michael Sacco, president of the Seafarers International Union, in a speech Tuesday to the group led by Gordon M. Ward that now claims to be the one true MEBA.Mr. Sacco later told The Journal of Commerce that he could envision an umbrella union that would have two separate groups, one representing officers and one ordinary seamen. In the past, maritime unions have sometimes battled fiercely for each other's jobs.

Mr. Sacco's union represents ordinary seamen.

Unity among maritime labor is essential if the unions are to survive the powerful threats over the next few years to the very existence of the U.S. merchant marine, said Mr. Sacco, echoing the comments of many other speakers at the Ward group's convention.

The labor leaders hope that by being unified and turning up the pressure in Washington in concert with marine employers in this election year they can get a national maritime policy on the books that will rebuild the U.S. merchant marine.

The two largest American lines, Sea-Land Service Inc. and American President Lines, have both said they will re-register their ships in other nations and employ foreign crews if a maritime policy is not approved.

"Nothing is going to get done in Washington unless the unions and the companies can agree on a maritime policy," said Mr. Ward in a speech Monday.

Mr. Ward's group held their first national convention this week across the street from the national convention being held by their opponents who continue to maintain they are the true MEBA. That opposing group is led by Andrew Cullison.

At the session on Tuesday, delegates to the MEBA convention organized by Mr. Ward voted to restrict membership in their union to engine, deck and radio officers employed on U.S.-flag oceangoing, Great Lakes and inland water vessels. The legal standing of these and other steps voted by the delegates may be subject to litigation.

The delegates' resolutions, if effected, would remove the influence of unlicensed mariners and shoreside workers from the engineers union.

The convention also elected Mr. Ward president of National MEBA, Ray McKay national secretary-treasurer and Lewis Smith national executive vice president. Mr. McKay is president of District No. 2-MEBA; Mr. Smith is a former president of District No. 3, the Radio Officers Union.

"The National Marine Engineers Beneficial Association is once again in the hands of licensed U.S. merchant marine officers," the three officials said in a joint statement.

In an effort to illustrate their differences with the past administration of C.E. DeFries, the delegates to the old-guard convention, organized by Mr. Cullison, adopted a resolution Monday prohibiting future severance payments to union officers.

Mr. DeFries and four other officers received some $2 million in severance payments after the 1988 merger with the National Maritime Union, but kept their jobs.

Monday's resolution was characterized by the Cullison group as a "reform designed to avoid future controversies" and not a repudiation of Mr. DeFries or the legitimacy of the payments he received.

Mr. DeFries was also named president emeritus of the union.

In his speech to the Ward group, Mr. Sacco warned that the battle for control of MEBA is far from over.

"You've got a long way to go yet," he said. "You have to be united . . . Don't let anyone see a crack in the fist," he added.

Every other seagoing labor union has pledged its support to the Ward group. District No. 2 of MEBA has defected and joined the Ward camp's convention, sources said.

Steve Chapman, a spokesman for Mr. Cullison, said he expects the backing of the (non-engineer) members of the merged union who came from the NMU.

"There was complete solidarity between the groups represented at the National MEBA convention," he said.

MEBA primarily represented ships officers until 1988 when a merger with the NMU brought ordinary seaman and large numbers of shoreside employees into the union, setting off four years of internal union strife.

The "second" MEBA was created in January when the Ward camp abandoned its strategy of seeking to have the 1988 merger voided by the courts and declared itself independent of the Cullison group, then led by Mr. DeFries.

"We learned the hard way," that legal challenges would not void the merger, said one member of the Ward camp.

Publicly, members of the Ward group say they are confident their strategy will make them victorious. Mr. Ward late Monday night predicted that the struggle would be over by August.

Privately, they concede that a victor has not been determined yet.

And they know if they lose, their jobs could disappear. "It's tough," said one Ward supporter. "I can't make any (financial) decisions in my life right now," the supporter added.

Key to the future legal battles will be the outcome of a referendum on the MEBA/NMU merger that will be completed within weeks.