General Dynamics Corp. reported a 1978 loss of $48.1 million ($4.51 per share) as a result of a negotiated settlement with the Navy over submarne contracts.

Sales for the year wree a record $3.2 billion, compared with $2.9 billion in 1977.

David S. Lewis, chariman and chief executive officer, said yesterday earnings from operations during 1978 were $138.6 million ($12.97), compared with 1977 earnings of $103.4 million ($9.51).

However, the gain in earnings was more than offset by the loss of $186.7 million, or $17.48 per share, because of a settlement with the Navy of a dispute over two contracts ot build SSN 688-class submarines.

Weyerhaeuser Co., the forest products giant, said yesterday it earned 74 cents a share in the fourth quarter, up from 49 cents a year earlier, on a rise in sales to $1.061 billion from $854.37 million.

Operating profit was 99 cents a share, but this was reduced 25 cents a share by the cost of settling civil class action antitrust lawsuits.

Operating profit of $3.19 a share for the year on sales of $3.8 billion was cut to $2.85 a share for the same reason, against $228 a share in 1977 on sales of $3.28 billion. Net income for the year was $371.14 million, up from $301.51 million.

Scott Paper Co. earned 84 cents a share in the fourth quarter of 1978, up from 20 cents a year earlier, on a spurt in sales to $464.82 million from $399.97 million.

Profit for the year was $93.56 million ($2.41 a share) on sales of $1.725 billion, compared with $99.2 million ($2.56) in 1977 on sales of $1.52 billion. However, 96 cents a share of the 1977 profit resulted from an accounting change.

The 1977 fourth-quarter profit was cut sharply by a special charge for the closing of a mill.