I read this book in 1989 and got it from my high school library. It had an interesting cover of a ship on the waters with a man and a woman on the cover looking at the sun. It was called something like underneath the sun or something to that effect but for the life of me, I can't find it anywhere regardless of the search term I use. I don't know what the exact year of the novel's publication was, but it couldn't have been more than 10 years earlier, so probably mid-late 70's to possibly mid-late 80's.
The story was about a pilot that crash lands on a planet and quickly finds that it's all women. They run everything and men are nowhere to be seen. Later he finds out that there are men and they are kept in very pampered conditions and used for, well procreation and maybe even pleasure but mostly as stud stock basically. The women have no problem being intimate with each other which is common and they are soldiers, leaders, so on and so forth, they run everything. So he is under the protection of this lady captain of a ship who finds his man-oriented world fascinating and gives him some slack to be more than the men they usually have.
He goes on quests with them, they find him very capable but ultimately he falls in love with the captain because he is not sure he will ever be able to leave the planet and might as well make the best of it. They find ruins that show evidence that maybe at some point this planet was more dominated by men but something catastrophic happened causing them to die off and so now they are a rare commodity. I remember I picked this up just on a whim and I couldn't put it down, it was far more interesting than I am able to convey here and I have always wanted to re-read it again as an adult with a lifetime of experience to see if my view of the story is still the same as it was when I read it the first time but no luck finding it. Any help would be greatly appreciated.