I can't find it online. I believe the scene you're looking for is from Mandingo 8, which is a worthwhile purchase since it also has outstanding sex scenes with Luci Thai and Lena Juliett as well.
In the meantime, I'd recommend this scene with another Nautica, Ms. Binx:
Mandingo Nautica Binx - Ebony sex video - Tube8.com
She's very beautiful and sassy, acting all impatient and saying "I'm ready for it". Then reality sets in. This is one of my favorites, though: they really groove on each other.