Navy Secretary John F. Lehman Jr. said yesterday that Adm. Hyman G. Rickover may have received "tens of thousands" of dollars worth of gifts from shipbuilders during the years he was running the Navy's nuclear submarine program.

Knowledgeable officials said the Pentagon has documented unreported gifts of jewelry, tie-pins, ship models and other items worth between $50,000 and $60,000. Other officials said the total may be higher than $150,000 once the Navy, Justice Department and congressional committees finish their investigations.

But the officials also said that Rickover, while allegedly keeping some of the gifts, also gave many to congressional officials and others.

Rickover, who as father of the nuclear Navy established a reputation for uncompromising honesty and commitment to quality, was previously reported to have received gifts, but on a smaller scale. Internal documents from General Dynamics Corp. showed that he received a $695 pair of diamond earrings and a $430 jade pendant in 1977.

The new information came as Lehman rejected allegations that the Navy is "sweeping under the rug" evidence of gift-giving to the retired admiral. Lehman said the Navy is investigating the gift-giving, which he said appears to have ended in 1978, and may try to fine the contractors involved or "debar" company officials who were responsible.

But he said that a proposal by Rep. John D. Dingell (D-Mich.), chairman of the House Energy and Commerce Committee, to cancel contracts with General Dynamics, the nation's largest defense contractor, and to suspend it from future business "would be cutting off our nose to spite our face."

"This kind of cry for blood ill befits institutions of our government that are supposed to defend civil liberties and civil rights rather than demanding drum-head justice," he said. "The facts that we have so far, the prima facie evidence, does not indicate anything of the magnitude that would warrant cancellation of the contracts . . . . "

Lehman said four companies appear to have given Rickover unreported gifts: General Dynamics, whose Electric Boat Division builds submarines in Connecticut; Newport News Shipbuilding & Dry Dock Co. in Virginia; Westinghouse Electric Co., and General Electric Co.

Knowledgeable officials said the statute of limitations has elapsed for any criminal charges that might have been considered against Rickover, ranging from conduct unbecoming an officer to more serious citations, or against the companies. But they said that, if the government can prove that the contractors used Navy funds to pay for the gifts, it could seek reimbursement and triple damages.

Rickover acknowledged in an earlier interview with probers that he accepted some gifts and that "over a period of years, it could add up to something." He said he did not believe it was wrong to accept the gifts, which he described as "mementos."

General Dynamics issued a statement last July saying that "there has been no wrongdoing at Electric Boat." The other three companies have declined comment on the more recent allegations.

Lehman's comments came at a news conference called to announce almost $2 billion in new ship contracts. He said the costs of the ships will be $243 million less than proposed in last year's budget because of Navy efforts to promote competition among shipbuilders.

"We are achieving, through our procurement reform, substantial underruns for the third straight year," Lehman said.

Contracts announced yesterday include down payments for four nuclear-powered attack submarines, three cruisers, two amphibious ships and the first of a new class of coastal minesweepers, Lehman said. Newport News won the right to build three of the submarines, compared with one for Electric Boat, because the Virginia company submitted a lower bid, Lehman said.