I've been behind a single 485...it sounded great. On my boat I have a pair of 80s (and a pair of MB8s) because it's a v-drive and I wanted to have a center walkway. But I think a single 485 would sound better than a pair of 80s because it has a larger horn than the 80s. For your boat, I'd go single 485 and not give it a second thought--you'll get better sound and the speaker will be out of the way. But if you're on the fence, you should contact Wetsounds and see what they think the difference will be re: sound.