Ted Turner begins final preparations today to defend the America's Cup of yachting - under a new cloud.

This time, the tsk-tsk arises from the Courageous skipper's disqualification from a weekend sailboat racing victory because he used a motor to avoid an accident. Turner's 61 1/2-foot pleasure craft Tenacious was far ahead of more than 100 competitors in the ocean race from Stamford, Conn., to Martha's Vineyard, Mass., and finished that way. But, near the halfway point off Cape Cod, Turner switched on Tenacious' motor to avoid hitting the Buzzards Bay tower - "It was for about five seconds; there was no wind and I figured if we hit the tower we'd break the mast and end up spending $50,000," Turner said."And we only saved the government a couple thousand dollars by not crashing into their tower."

Turner said ocean racing rules allow use of a motor in emergencies but he felt race officials cracked down on him because he is in the spotlight as 12-meter defender vs. Australia - "If they hadn't said anything, they probably would have been accused of favoritism."

While Turner, suspended owner of the Atlanta Braves, tried to shrug off the sour finish to the "mental vacation" he said the two days of 'round-the-clock competitive sailing meant to him and his Neeewport match-racing crew. Turner employee Hank Aaron did some shrugging off too. Aaron, a Brave veep, allowed that Sadaharu Oh deserved praise for passing Aaron's total of 755 major league home runs - and he'll go to Japan for congratulatory ceremonies - but, "It can't be the baseball probably is two steps down." major league record . . . Japanese Bowie Kuhn, the man who suspended Turner, recently declared in a further demonstration of "clout" that O'hs home run mark will not be recognized in the U.S. - bringgging us to the real punch line from the usually agreeable Aaron: "For the first time, I agree with something the commissioner says." Oh, Henry!...