For Billy Davis Jr. (left) this is not the first time he's walked the plank for his woman. Just 18 months ago Marilyn McCoo and Davis were striking out alone as an R&B (as in Risky & Beware) act after a successful decade and 20 million records as two-fifths of the Fifth Dimension. "Everyone thought we were crazy," admits Bill. "But we said, 'Let us do it, and we'll show you.' "

And they did. Though the famous likes of Jermaine Jackson, Eddie Kendricks and even Smokey Robinson fizzled commercially after splitting from soul groups, Bill, 39, and Marilyn, 32, are reversing the odds. In the first year on their own they've produced a gold album, I Hope We Get to Love on Time, and a No. 1 single, You Don't Have to Be a Star, which also copped a Grammy. Last month they won the $10,000 grand prize at the Tokyo Music Festival. They're currently winding up a six-shot summer series on CBS.

The latter, to be sure, is their one career embarrassment so far. With leaden ratings (even opposite Donny & Marie reruns) and lame comedy routines, McCoo and Davis hardly have to fret, as they once did, about being labeled "the black Sonny and Cher." "Billy and I are used to doing things over until we get them right," Marilyn rationalizes. "In TV you don't have that freedom. Besides, we're not early-morning people and we had to get up at 6:30 a.m. for the show."

Their resiliency is at least partly due to the fact that McCoo and Davis were a couple long before they became a duet. They met 11 years ago when singer-photographer Lamonte McLemore hired Billy, Marilyn, Ron Townson and Florence LaRue Gordon to form the Fifth Dimension.

The group clicked with singles like Up, Up, and Away, but McCoo and Davis did not. "I saw Billy as this street cat who thought he was superhip," Marilyn remembers. "I wasn't interested." Billy, in return, "thought she was very square, very naive." According to Marilyn, "Our respect for each other as performers grew first, then we got to know each other as people. We had no acts up, no guards or games going, because we were not trying to impress each other."

"After we did get each other's confidence," Billy adds, "we started trying to change each other. That was our biggest mistake." Their first two years together, Marilyn agrees, "were very stormy. We argued constantly. The others in the group never thought we'd get married." They finally got to love—and church—on time in 1969.

Marilyn is the middle daughter of two well-to-do doctors who migrated from New Jersey to Georgia to L.A. (Older sister Glenda is an L.A. TV newscaster; younger sister Millie is a USIS official in Madagascar.) Marilyn started singing in school shows at 7 and in public at 12. "Once my parents realized I was serious about show business," she recalls, "they had me taking voice and dancing lessons from then on." She turned up on Art Linkletter's Talent Scouts and won the talent prize in the "Miss Bronze California" contest. After picking up a business administration degree from UCLA and working for a poverty program in Watts, Marilyn joined McLemore (briefly her offstage partner as well) and the Fifth Dimension.

Davis was the sixth of seven children born to a St. Louis furniture salesman. (His dad is now co-owner with Billy of a record store and his son's enthusiastic promoter during hometown visits.) Like Marilyn, Bill began singing in grade school and, unlike Marilyn, at his Baptist church. He formed R&B groups at Washington Technical High School and eventually married his teenage sweetheart. (Later amicably divorced, they have a son, Steven, 13, who lives with Marilyn and Billy but visits his mother in Detroit every summer.) In 1965 Billy moved to L.A. and broke into the Fifth Dimension a year later.

Even after the group split, Billy and Marilyn remained on good terms with the other members (except Florence). "With the group we were using maybe one-third of what we had to offer," Marilyn says. "It was time to leave." (Their decision was helped, they say, by Werner Erhard's est seminar.) At first they had planned solo careers. "His voice is funky and soulful, and mine is kind of straight pop," she points out. But they decided to blend their styles, he adding a ballad side and she a raw edge to one of the smoothest voices in pop. "We realized," she continues, "that if we headed in separate directions we'd be apart from one another. We wanted to be happy in our careers but also to keep our marriage together."

Now McCoo and Davis have the best of both worlds in their ranch house in suburban Encino, Calif., equipped with both pool and tennis court. (They experienced a sort of sick recognition earlier this year, however, when a cross was burned in their yard—and those of other blacks in predominantly white Los Angeles neighborhoods.) A housekeeper watches Steven when they're on the road.

Marilyn has decided against motherhood herself, "even though my whole upbringing was toward having children. My gut feeling was that they'd slow me down in my career. But I'm glad we have Steven. Having a child in your life opens up so much more for you."

This summer Marilyn and Billy are on the lucrative state fair circuit (a coup itself for a new act) and have a second LP, The Two of Us, coming out in August. Marilyn is looking over movie offers, and they're booked into Vegas. Already they've raised the specter of being called "the black Steve and Eydie." Marilyn and Billy haven't suggested it yet, but some young singing couple of the future could do worse than be known as "the white McCoo and Davis."