The chairman of the Federal Home Loan Bank Board told a congressional subcommittee yesterday that if the agency tried to resolve the thrift crisis immediately, without extra funding being provided, the insurance fund would run out of money in less than a year.

Although U.S. savings institutions are expecting record profits this year, the Federal Savings and Loan Insurance Corp. finds itself in a very grave situation, FHLBB Chairman Edwin J. Gray said. The FSLIC is run by the bank board.

The insurance fund, which protects deposits at savings institutions up to a limit of $100,000 each, has only $3.2 billion in reserves available for future losses. At the same time, 300 thrifts -- or about 10 percent of the industry -- with $90 billion in assets, are insolvent or are expected to become so in the next year. And the agency lists 900 institutions as seriously troubled, but not insolvent, he told a House Banking subcommittee.

On top of those difficulties, outstanding and projected income capital certificates -- government IOUs used to prop up the bottom lines of ailing thrifts -- could draw down the fund by another $1 billion, Gray added.

According to Gray, the thrifts' difficulties stem less from portfolios of old, low-yielding mortgages than from bad loans and risky investments, the products of deregulation. The most vulnerable are state-chartered thrifts in the Sun Belt, some of which have put depositors' money into such enterprises as a mushroom farm, a tire-retreading factory and boats used to ferry gamblers to a lakeside resort, he said.

Gray presented several potential remedies to the agency's dilemma, while noting, "We have nothing but poor choices under the circumstances." He virtually dismissed retaining the status quo; a taxpayer bailout, or a merger of FSLIC with the Federal Deposit Insurance Corp., which insures banks. Instead, he talked about another alternative: recapitalization of the fund, which Congress could acccomplish by granting the agency authority to collect an amount equal to 1 percent of the deposits of each of the insured savings institutions. When he stressed, however, that Congress should pick the remedy, one legislator reminded him that they would be unlikely to act without a board consensus.

The recapitalization plan would add about $8.5 billion to FSLIC's reserves. These funds would be counted as assets until they were used to assist troubled thrifts, at which time they would become expenses. However, the board's general counsel said yesterday it is not clear whether the funds could legally be used directly to help failing thrifts.

The thrift industry strongly opposes this plan, which was modeled after the solution that credit unions accepted a few years ago to ease their troubles. The thrifts complain that healthy institutions would be subsidizing ailing ones. To placate sound institutions and not penalize those that are prospering, insurance premiums would have to be scaled according to risk, Gray said. Even so, some healthy thrifts might leave FSLIC and become banks, rather than pay this price.

That would put the burden on troubled thrifts, which can afford it least.

In 1982, Congress pledged the full faith and credit of the United States to back deposit insurance. Chairman Fernand St Germain (D-R.I.) warned yesteday that the Gramm-Rudman balanced-budget amendment effectively would negate this statement of congressional intent. He called on the administration to say what would happen to FSLIC and FDIC if the amendment passes.