Despite success with sales of its Renault Alliance, American Motors Corp. yesterday reported a net loss of $66.1 million for the first quarter of the year compared with a loss of $51 million in the comparable quarter of 1982.

In other earnings results:

* Sears, Roebuck and Co.'s first-quarter profit rose 130 percent from a year earlier to set a record, mainly because of improved retail merchandising and higher income from the company's investment subsidiary, the nation's largest retailer reported yesterday.

* Coca-Cola Co. profits increased by 13 1/2 percent as revenue went 19.4 percent higher, with Columbia Pictures Industries Inc. contributing "significantly" to the advance.

* American Brands Inc. profits increased by 2 percent, led by a 9.2 percent gain in pretax income from tobacco operations--the company's largest business--to a record $132.5 million.

* Merrill Lynch & Co. Inc. net earnings more than quadrupled from a year ago to $127 million and revenue rose 39 percent on record stock market volume.

* Boeing Co. profits and revenue rose by about 50 percent, mainly because of higher sales volume and lower expenses for new jet transport programs.

* Standard Oil Co. (Indiana), the nation's 6th-largest oil firm, blamed a 15 percent decline in its first-quarter profits on stiff competition in the U.S. gasoline market, while Union Oil of California, ranked 14th, had a 24 percent decline in first-quarter profits, and Ashland Oil Co., ranked 16th, announced a $14.5 million loss for the first three months of 1983.

AMC Chairman W. Paul Tippett said that the automaker "stated several weeks ago that we expected to lose money in the first half of 1983--more than the first half of last year--as a result of reduced international sales, heavy launch costs for new products and other expenses such as those associated with the phase-out of our rear-wheel-drive passenger car lines."

Tippett also said export sales were weak in the first quarter because of currency devaluations and dropping oil revenues in some of AMC's key overseas markets.

"The highly successful Renault Alliance spearheaded a sharp increase in our passenger-car retail sales, and a 30 percent production increase was just announced," he added. Sears, Roebuck and Co. earned $164.6 million (47 cents a share) in the quarter compared with $71.4 million (20 cents) in the comparable period last year. Sales rose to $6.91 billion from $6.44 billion.

The retail merchandising unit recorded a profit of $16.2 million compared with a $23.2 million loss last year, the Allstate Insurance group earned $135.7 million compared with $116.1 million, the Dean Witter financial services group had a $40.2 million profit compared with a $7 million loss, and the Coldwell Banker real estate subsidiary, earned $3.3 million compared with a $2 million loss. Coca-Cola Co. net income was $122.13 million (90 cents a share) compared with $107.62 million (87 cents) for the first quarter of 1982. Revenue increased to $1.52 billion from $1.27 billion.

The company said syrup and concentrate shipments increased 8 percent in its Coca-Cola USA division, and that sales of Diet Coke continued to exceed expectations. Overseas, Coca-Cola said unit sales for the quarter increased in all major markets except Latin America, with increases ranging from 40 percent in the Philippines to less than 5 percent in Europe and Africa.

In its food and wine sector, Coca-Cola said unit sales of coffee, chilled citrus and Hi-C products increased, while unit sales of frozen juices declined. Price competition from domestic and foreign producers also cut into profits of the company's Wine Spectrum division, it said. American Brands Inc. earnings rose to $97 million ($1.67 a share) from $95 million ($1.63) a year earlier. Revenue rose to $1.79 billion from $1.70 billion.

American Brands makes Lucky Strike, Carlton, Pall Mall and Tareyton cigarettes. It other businesses include liquor, office products, golf balls and biscuits. Merrill Lynch & Co. Inc., the nation's largest brokerage house, said that earnings zoomed to $127 million ($3.07 a share) from $30 million (76 cents) a year ago, as revenue soared to $1.4 billion from $1 billion. Per-share earnings do not reflect a two-for-one stock split declared Sunday and payable June 27 to stockholders of record June 1.

The company also announced an 11 percent increase in its quarterly dividend to 40 cents a share from 36 cents in the past two quarters and 32 cents a year ago. The dividend will be paid May 25 to stockholders of record May 1.

Commission revenues on securities and other trading operations were up 93 percent from a year ago at $411 million, revenue from principal trading transactions climbed 89 percent to $221 million, investment banking revenue advanced 114 percent to $188 million, real estate revenues rose 63 percent, and insurance revenues were up only 2 percent. Boeing Co. profits increased to $90 million (93 cents a share) from $61 million (63 cents) a year ago, as sales grew to $2.98 billion from $2.08 billion. Standard Oil Co. (Indiana) earned $399 million ($1.36 a share) compared with $470 million ($1.60) in the same three months last year. Revenue slipped to $7.5 billion from $7.2 billion. Union Oil Co. of California earned $128.3 million (74 cents a share) compared with $168.5 million (97 cents) a year earlier. Revenue slipped to $2.47 billion compared with $2.48 billion. Ashland Oil Co., which is the largest independent refiner, said its loss of $14.5 million for its second quarter ended March 31 compared with a $11.6 million loss a year earlier. Revenue tumbled 18 percent to $1.8 billion from $2.2 billion.

Six-month income totaled $14.6 million compared with $35.9 million in the same period last year. Revenue fell to $3.9 billion from $4.6 billion.