The Reagan administration went on record yesterday in opposition to a bailout a la Chrysler for the savings industry. It believes the current system of government-directed mergers and very limited capital infusions is adequate to get troubled thrift institutions through their immediate crisis until interest rates decline.

Treasury Assistant Secretary Roger W. Mehle Jr. told a House banking subcommittee hearing that proposed legislation is unnecessary and could hurt part of the thrift industry without effectively helping the housing industry.

Rep. Fernand St Germain (D-R.I.) has proposed having the Federal Home Loan Bank Board pump up savings and loans' net worth to the required 2 percent of assets for up to five years by issuing income capital certificates. The certificates would only be converted into cash if the institution failed. To date, only four S&Ls have received such cashless infusions.

The savings industry prefers this approach over forced mergers of thrifts whose net worth has fallen below the required level. In 1981 there were 294 mergers of S&Ls, a quarter of them ordered by regulators. Yesterday, Bank Board Chairman Richard Pratt predicted that even if interest rates drop by two percentage points, 1,051 S&Ls will decline to 2 percent net worth in 1982, and 200 will run out of capital. In 1983 the number of S&Ls would reach 1,829, with 300 having exhausted their net worth, the point at which liabilities equal assets.

A law mandating that the government prop up these S&Ls' net worth would give them no incentive to cut costs. Moreover, Pratt pointed out the possibility that S&Ls currently above 2 percent net worth would sell off their low-yielding loans at a loss to get a capital infusion.

Both would limit the bailouts to selected institutions with a good chance of success, a tactic the industry considers to be "playing god."

Pratt gave conditional support to the bill, provided long-term measures to grants thrifts additional lending powers are also the subject of future legislation. (St Germain predicted yesterday it would be more difficult than ever to reach a consensus on restructuring the financial industry following creation last Monday of a new savings certificate for thrifts, a move that angered banks.)

William M. Isaac, chairman of the Federal Deposit Insurance Corp., which insures mutual savings banks, expressed a preference for mergers over capital infusions, saying subsidies perpetuate weak management. If there are to be subsidies, however, Isaac suggested that a maximum be set, "and either the thrifts make it or they don't." Otherwise it would take $1 billion in capital certificates to bring the thrifts up to 3 percent net worth. While that amount would not figure in the budget, the interest to be paid on it would.

Isaac also demanded management control over subsidized thrifts. "We do not believe that an institution should receive taxpayer funds and then simply continue to do business as usual," he said.

One question rarely discussed publicly is whether, if ultimately necessary, the thrifts should be sacrificed to save housing or vice versa. Yet it surfaced yesterday.

The officials warned that if thrift institutions were required to put 50 percent of net new deposits into mortgages with low interest rates, as stated in the proposed legislation, they would lose even more money. St Germain said this provision was included because "the American people must believe this bill is not just designed to preserve thrifts, but also to help housing."

Isaac said, "The marketplace will provide funds for housing, whether it be thrifts, commercial banks or Sears, if it makes economic sense."