This could possibly be End of Exile (1975) by Ben Bova, the last novel of his Exiles trilogy.
The novel follows Linc, one of a group of teenagers born on and living in a spacecraft that is meant to carry them from Earth to a habitable planet, although the teens are not really aware of their circumstances. They live and farm in the outer sections of the deteriorating vehicle, forbidden to explore or try to tinker with the machines around them—even as those machines are failing. All they have to guide them are a handful of prerecorded video messages left by Jerlet, the last adult left alive on board. When Linc tries to fix a broken machine, he is cast out by Magda, the group's leader, who has become a priestess reiterating Jerlet's words.
Exiled among exiles, Linc discovers that he can find his way inward into empty sectors of the ship. He ultimately finds Jerlet, who is still alive, but who had to move to the center of the rotating ship—where the artificial gravity is negligible—because of the weakness of his failing heart. Eventually, with Jerlet's help, he is able to prepare the teens for the ship's upcoming arrival at their destination, the habitable planet of Beryl.
All three books in the Exiles series were aimed at young audiences, but the first two, Exiled From Earth and Flight of Exiles centered around adult characters and thus had a rather different feel from End of Exile, in which is dominated by teens. The first two books are also fairly hard science fiction, while the last book introduces teleportation technology seemingly out of nowhere. Of course, Bova was not, in general very concerned with maintaining any particular kind of unity in his multi-book series, and, in fact, all three books could be read essentially independently. (For example, they have no characters in common; the very first thing that happens in Flight of Exiles is the sudden death of the main character from Exiled From Earth.)
