Despite an increase in sales, Crown Central Petroleum Corp. reported a 56 percent drop in profits for the third quarter of 1983, with the company's net income totaling $3.6 million (50 cents a share) compared with the $8.4 million ($1.16) earned during 1982's third quarter.

Revenues for the same period totaled $472.7 million, compared with revenues of $451.7 million reported for the third quarter of 1982. Revenues climbed largely because of the company's acquisition at the beginning of the third quarter of the Zippy Mar and Fast Fare convenience store chain.

Sales of petroleum products also increased, noted Crown Chairman Henry A. Rosenberg Jr., but profits were "affected by the continuing downward pressure on gross margins," the company said.

"For the first nine months of the year, the company incurred a net loss of nearly $3 million (-63 cents), compared with the $2.4 million (23 cents) profit earned during the same time period in 1982. Revenues for the first nine months of 1983--$1.174 billion--were also down compared with last year when sales totaled $1.284 billion for the first nine months.

An improving economy and lower fuel costs pushed profits up 51 percent for the Richmond-based Overnite Transportation Co. for the third quarter. Earnings were $8.9 million (65 cents) compared with $5.9 million (43 cents) for the same three months in 1982. Revenues were up 20 percent--from last year's $74 million to $88.8 million this year.

For the first nine months of the year, the trucking company's profits were up 60 percent over the first nine months of 1982 --$22.1 million ($1.63) from $13.8 million ($1.02), as revenues for the same time period rose 16 percent, from $215.8 million to $250.1 million.

SYSCON Corp. reported an increase in both revenues and profits for the third quarter, with earnings climbing to $915,000 (31 cents), a 20 percent increase over 1982's third quarter earnings of $759,000 (28 cents). Revenues for the quarter climbed 18 percent over last year, from $18.5 million to $21.9 million.

For the first nine months of the year, the computer-software firm earned $2.4 million (86 cents), a 30 percent increase over the $1.8 million (68 cents) in profits earned during the same time period last year. Revenues were up more than 16 percent, from $52.2 million to $60.9 million.

Evaluation Research Corp. reported a 46 percent increase in profits for the third quarter--$242,000 (8 cents) compared with $165,000 (9 cents) last year. Earnings per share were less however, because of a stock split in June. Revenues for the third quarter totaled $7.4 million, up 34 percent over last year's $5.6 million. The professional services firm said that for the first nine months of the year, profits more than doubled--growing from $420,000 (24 cents) to $908,000 (30 cents). Revenues for the first nine months of this year totaled $22 million compared with $14.4 million last year.

Scope Inc. reported a 70 percent drop in earnings for the third quarter--$14,000 (1 cent) compared with the $47,000 (17 cents) the company earned during 1982's third quarter. Third quarter sales were also down, about 6 percent, from 1982 levels, from $3 million to $2.8 million. For the first nine months of the year, the company earned $244,000 (20 cents), compared to the $454,000 loss (38 cents) the company incurred during the same time period in 1982. The improvement came despite a drop in earnings, from $8.5 million for the first nine months last year to $7.5 million this year.

UNC Resources Inc. of Falls Church yesterday reported it cut its third quarter loss from $4.2 million (37 cents a share) to $118,000 (1 cent), as a result of collecting $7.8 million in a lawsuit.

UNC said it lost money in its shipbuilding, machine tool and offshore oil equipment businesses during the third quarter. The earnings announcement indicated UNC's quarterly loss would have widened rather than shrunk, had the company not collected a windfall in court. UNC did not report earnings exclusive of the court settlement, but noted it made a pre-tax gain of $4.8 million on the lawsuit; also included in quarterly earnings was a gain of $1.9 million from sale of an affiliate and a $1 million loss on sale of oil property.

Quarterly revenues from UNC's operations slipped slightly, from $60.7 million to $60.2 million, and for the first nine months of the year were down to $204.4 million from $269.8 million. For the nine months, UNC lost $1.2 million (10 cents), compared with a loss of $7 million (63 cents) in the same period a year ago.

TU International Inc. reported a 65 percent drop in profits for its fiscal year that ended June 30 from the previous year--despite nearly doubling its revenues during the same time period.

Audited results announced Friday by TU show the Falls Church computer equipment distributor earned $182,560 (4 cents) for the latest fiscal year, compared with the $534,608 (17 cents) earned the previous year.

Revenues for the latest fiscal year totaled $25.7 million, compared with revenues of almost $13 million for 1982.

Pargas Inc. said its profits declined in the latest quarter because of the unseasonably warm weather and drought.

Pargas' earnings for the quarter ending Sept. 30 were $117,000 (2 cents), compared with the $2.8 million (66 cents) earned during the same period last year. Revenue for the third quarter were up only slightly over last year--$60.5 million compared with $60.1 million last year.

Pargas' earnings for the first nine months of 1983 totaled $6.2 million ($1.50), down 21 percent from the $7.9 million ($1.90) earned during the same period last year. Revenues for the nine-month period were $215.7 million this year, up 11.5 percent from last year.