Mortgage Rates See Sharpest Jump in 18 Months : Loans: The average interest rate on 30-year fixed mortgages climbed to 8.82% from 8.65%. The move is pushing many consumers to lock in their loans.

Mortgage interest rates posted their sharpest jump in 18 months last week, sparking a move by consumers to lock in their loans as interest rates head back toward--and in some cases through--the 9% level.

The average rate on 30-year fixed mortgages climbed to 8.82% from 8.65%, according to preliminary results of a survey by HSH Associates in Butler, N.J. It was the largest weekly jump since August, 1990.

Mortgage rates at California’s major lending institutions typically rose two or three tenths of a percentage point, weekly surveys show, but some fixed-rate loans rose more than a half of a percentage point.

Interest rates on 30-year, fixed-rate loans--including finance charges and fees--are now well above 9% at Bank of America and Home Savings of America, two of the state’s largest mortgage lenders.

The rise partly reflected a jump in bond yields, which soared last Wednesday after Federal Reserve Board Chairman Alan Greenspan indicated that further rate cuts were not imminent.

The run-up, amid a refinancing boom, nudged “a tremendous number” of consumers with applications pending or approved to lock in rates, said Anthony Schweiger, president of Meridian Mortgage Corp. in Wayne, Pa.

Overwhelmed lenders have also raised mortgage rates in an effort to dampen loan demand, said one real estate broker in San Diego.

“Lenders have so many loans in the system that this is their way of saying: ‘Enough,’ ” the broker said. “They can’t handle it.”

The rise in rates means that lenders who sell their new mortgages to the secondary market are in danger of seeing the value of their inventory decline, experts said. Many have loans in the mortgage pipeline that are not yet ready for sale.

“If a lender didn’t hedge, it could be very costly,” said Dennis Jacobe, managing director of Financial Research Institute in Washington.

Mortgage bankers say they typically hedge by entering contracts to sell loans at future dates at specified prices.

“I do believe there was some scrambling for coverage over the past week,” said John Philips, a senior vice president at Crestar Mortgage Corp. in Richmond, Va.

Meanwhile, the rate turnaround may moderate the breakneck pace of new loan applications. “The pace is slowing from torrid to frenzied,” said Richard Peach, an economist for the Mortgage Bankers Assn. of America.