The Federal Savings and Loan Insurance Corp., already facing a financial crisis, lost another $193 million when it closed San Marino Savings & Loan in California last week.

The loss was the largest ever incurred in an outright liquidation, although larger losses have resulted from involuntary mergers of failing institutions.

Mergers have been used 17 times this year and liquidation nine times in government regulators' efforts to preserve the troubled savings institution system. Unlike past failures, most this year involved bad loans and rapid growth without adequate capital. The failures have placed a burden on the insurance fund, which is said to have declined to an estimated $6 billion.

San Marino, which the government seized on Feb. 3, was reopened last Monday as Community Federal Savings. Before the transformation into a federally chartered institution, the S&L's real estate assets with a face value of $220 million were sold off for $15.6 million. San Marino had a negative net worth of $58.4 million. It had also borrowed $645 million from the Federal Home Loan Bank of San Francisco and held $5 million in uninsured deposits. Its assets had also increased by 30 percent in the 10 months since it was seized, largely because of prior commitments.

The regulators contended they were unable to find a buyer for San Marino or to resolve its problems. According to the Wall Street Journal, more than a dozen potential buyers had earlier made offers to the government, but their offers were not accepted. San Marino's former owners charged that by the time the government solicited bids in September, it had no capital left.

San Marino's case fits the pattern of abuses the Federal Home Loan Bank Board has tried to cure. On Monday, an FSLIC representative said there are "hundreds of thrifts that are grossly undercapitalized."

Of the thrifts that have failed this year, the "overwhelming majority" were involved in direct investment in real estate development and other ventures. And 90 percent of the new cases involve asset quality problems. Consequently, said the FSLIC representative, the insurance fund is moving to levels approaching the record low ratio of funds to insured deposits of the 1960s.