Here's the line again:

In reply to:

Jerry hooted as he whipped the car around.


OK. I hear that, Fish, as a hoot--or a whoopee, as I wrote--but as you pointed out, I've never heard whoopee used as a verb--only as an interjection. So, if I were bound and determined to use whoopee in this context, I'd really have to change the rhythm of the sentence and write:

Jerry shouted, "Whoopee!" as he whipped the car around......but I don't like that nearly as well as the original Jerry hooted as he whipped the car around. I was just making the point that when one hoots, one makes a sound, I would imagine, similar to Whoopee. Now that I think about it more deeply--glad I'm spending my morning this way, by the way--I don't think Whoopee is good at all. I like the hoot.