James Parker is a well-connected Boston real-estate man who raises Irish setters, and skippers the 37-foot auxiliary ketch Platina out of Marblehead. Because he is also a man of considerable patience and energy, and generous with his time, he has spent much of his life in the show ring judging dogs and on committee boats supervising sailboat races. Now Parker's steadfast devotion to boats and dogs has brought him an unusual distinction. As the president of the Eastern Dog Club he has just staged a highly successful renewal of its annual show in Boston. And as the just-elected commodore of Marblehead's Eastern Yacht Club, one of the most active and prestigious yachting bodies in the country, he is currently planning the final trials, to be held off Marblehead this summer, to determine who will represent the U.S. in the Olympics. Skippers from all over the country will converge there to sail their 5.5-meter and Finn Monotype class boats. "All eyes will be on Marblehead," says Parker. "It will be fun."