Wildcat strikes by coal miners reduced Chessie System coal shipments by half and caused profits to plummet in the quarter ended Sept. 30, the railroad company reported yesterday.

Chessie earned $5.7 million (28 cents a share) in the third period of 1977 compared with $22.2 million ($1.17) a year earlier. Revenues for the firm's three railroads - Baltimore & Ohio, Chesapeake & Ohio and Western Maryland - rose to $370 million from $351 million.

Chairman Hays T. Watkins emphasized, in a statement, his view that Chessie's "basic earning power continuse intact," that the outlook for future business is "encouraging" and that the railroad's current dividend rate faces "no threat" because of lower profits.

Strikes by various coal miner groups continued over a 10-week period of the recent quarter and were concentrated in states served by Chessie, the largest coal-hauling rail frim in the nation. Moreover, the outlook for coal traffic is uncertain with current contracts between mine operators and the United Mine Workers expiring Dec. 6.

Because of the recent strikes and a first-quarter loss related to record cold weather, Chessie's year-to-date performance is lagging behind that of 1976. Nine-month profits totaled $47.7 million ($2.48 a share) vs. $65.3 million ($3.44). Revenues rose to $1.1 billion from $1.05 billion.

Watkins said one factor contributing to lower profits was a decision to continue with planned roadway and equipment maintenance projects despite reduced freight traffic.

Solon Automated Services reported earnings of $1.068 million for its third quarter ended June 30, up from $957,000 for the same period a year ago, as revenues grew from $11.2 million to $12.5 million. Earnings per share were 37 cents against 34 cents the year before.

Solon, which makes and leases coin operated laundry equipment, increased its dividend in August from 2 to 3 cents a share.

Manor Care, Inc., a nursing homeservice firm based in Silver Spring, reported profits in the first quarter ended Aug. 31 of $158,000 (10 cents a share), off sharply from $990,000 (59 cents) in the same period a year ago. Revenues rose to $8.4 million from $7.3 million.

President C. Houston McCeney said the principal factors in lower first quarter earnings were startup expenses associated with five new facilities and losses at two subsidiaries. In addition, the previous year's quarter included 46 cents a share from the sale of assets.