Buddy Ebsen, who tap-danced across many a Hollywood ship deck in World War II musicals, donated two catamarans to the Naval Academy, challenged the commandant, Rear Adm. K.R. McKee, to race and beat him two out of three Sunday.

So? So what better introduction to the sea-shaking news that the New York Yacht Club has closed challenges for the America's Cup with a record six foreign outfits in the fray for 19 0. Undaunted by the 22 successful U.S. defenses in 22 tries since 1870 are two French hopefuls (Yacht Club d'Hyeres - yes, the intrepid Ball-Point Baron Marcel Bich yet again - Societe des Regats Rochellaises); two from Australia (Royal Sydney Squadron and Royal Perth Squadron); one from Sweden (Royal Y.C. of Gothenburg), and the first English bid since 1964 (Royal Southern Y.C.).

Only two years till trials . . . .

And only four days til Seattle Slew runs again, if, as planned, he goes in a seven-furlong tuneup at Aqueduct on Sunday . . . .

The Consumer Product Safety Commission reports that the manafacturer of 7,500 baseball pitching machines has agreed to fix a defect allegedly responsible for at least 35 serious injuries. Master Pitching Machine Inc., maker of the "Dudley" and "Commercial Mechanisms" apparatus, by consent in federal court agreed to provide a metal screen guard to prevent the pitching arm from hitting someone of it accidentally swings. For further information, call CPSC, toll-free, at 800-638-2666 or, in Maryland, 800-492-2937 . . .

NBA rookie of the year, by vote of media in league cities: Phoenix former Tar Heel, forward Walter Davis, 49 1/4 votes to 10 1/4 for runner-up Marques Johnson, the Milwaukee Buck who outshone him in the playoffs (after the balloting) . . Still pound for pound the greatest boxer of all time by vote of the Boxing Writers of America: Sugar Ray Robinson, 40 to 13 for runner-up Muhammad Ali - who despite that was elected only No. 2 heavyweight. JKOE Lous beat him, 35-27, adding glow to the Omni Awards inaugural coming at the Hyatt Regency on Saturday, at which the $100a-seat guests honoring the Brown Bomber by long distance (he'll be at the casino where hekis employed in Las Begas) are supposed to mingle with Ali and Leon Spinks, if all goes well. Other greatest of all time: light heavy Archie Moore, Robinson in both middleweight and welter divisions, and one current champ, Roberto Duran, outpolling - say it ain't so - Benny Leonard and Henry Armstrong . . .

Item from New York: Talks involving a proposed series of three-round exhibition bouts on five consecutive June nights at Madison Square Garden between Ali and Teofolio Stevenson, Cuba's Olympic champ "have been broken off," says Mike Burke, Garden president. What, he rang up Cuba and was hung up on? . . .

Ho-hum. Here's Jim Bouton again, down to pitch during tonight's Atlanta-Richmond Braves exhibition in the Virginia capital - and the big club's An erica's Cup yacht champ, Ted Turner, umpiring at third base.