I'm confused on the acceptable maximum word count for Young Adult manuscripts. Different publishers seem to want different things and word count is all over the place. Covenant says they want the word count to be no more than 70,000 (or so I've been told), but Deseret Book has specifically told me they have no set word count. Twilight was definitely way over the 70,000 as are the Harry Potter books. Can you give me a good figure for this? Or is it different depending on each genre?
The size of a Middle Grade or Young Adult novel used to be under 40,000 to 70,000 because publishers didn't believe children and teens would read "big" books. Twilight and Harry Potter sort of blew that theory out of the water. Now, publishers are willing to look at longer books for a young audience.
Write your book. Make it as long as it needs to be to tell the story well. Then start looking for a publisher or agent who will take a YA book at your word count.
That said, if you're a brand new author, the closer your YA manuscript is to 70-90,000 word count range, the better.