The boating publication industry soon will be operating without a Rudder.

Rudder, at age 93 the oldest yachting magazine in the nation and perhaps the world, will expire with the July issue, its associate publisher confirmed Friday.

Once the preeminent publication in its field, Rudder fell on hard times after CBS bought and regionalized it in 1977. At the time, it had a healthy national circulation of about 120,000, according to its former editor, but, as an Eastern regional publication, it never took off.

The foundering magazine was sold three years ago to Petersen Publications of California, which moved Rudder's headquarters from Connecticut to Annapolis. The move was hailed locally as an indication of the growing significance of the Chesapeake Bay as a yachting center, but Rudder's advertising revenues continued to fall. Circulation recently had dropped to about 42,000, according to editor Diego Kahr.

Its demise will be mourned by boat fanciers who remember simpler times, when instead of the current crowd of publications there were only two significant boating magazines on the market, Rudder and Yachting, with clear and quite different philosophies.

Rudder was founded in 1890 by Thomas Fleming Day, whose aim was to provide nuts-and-bolts information to boaters of moderate means. The magazine published stories on small-boat design, how-to features and seagoing adventure stories. His editorial policy prevailed for more than three-quarters of a century.

In May 1915, Day wrote, "From the first, Rudder played to the small man, the little fellow, the real boat-sailor, water-lover and enthusiast, and among these men we found friends and supporters."

Petersen Publications, which publishes other successful magazines including Motor Trend and Skin Diving, will continue in the boating field with two other regional offerings, Sea & Pacific Skipper (West Coast) and Lakeland Boating (Midwest), Kahr said.

The last editor of Rudder, when it was still a national publication, was Marty Luray, who now works at Sail, the current top-selling publication in the field with a circulation of 178,000. Luray said 1977 was the end of the glory days for Rudder. "When it was split up, the demise began," he said.

Others in the industry maintain that Rudder was a victim of changing times. Its emphasis on do-it-yourself techniques became less appealing, they said, with the advent of fiberglass boats, which require less maintenance than their wooden predecessors.

And they said Rudder failed to rise to the challenge of specialization when new magazines chipped away at its readership.

"The publications have become more directed," said Sail editor Keith Taylor. He cited such specialized magazines as Woodenboat, Cruising World and Small Boat Journal.