Nothing looks better than an antique outboard on an outboard-designed wooden boat.
I picked up this 1957 Mercury Mark 55, 40 h.p., from Ebay. It came from Wisconsin for $285, with shipping, via UPS! It was a dreadful mess on the outside, but turns out the upper end was great. Fired right off. But spent a good bit on the lower unit, getting a nearly complete re-sealing and water system overhaul. Then had a friend who is an auto bodyman do the finish work.
The biggest problem you'll run into is finding parts, but perhaps you'll be lucky like I was on labor: The mechanic I brought it to charged me next to nothing, saying, "After working on all this new stuff, it's been a pleasure to mess with this simple, old engine."
Good luck with it.
"And look at Elias Wonder. Yeah, take a gander at that buzzard. Forty years ago he was happy, generous, charitable, tall, dark and handsome. Then he took up the fly rod. Now consider him. Uglier than fresh road kill. Evil-eyed, cantankerous, sullen, mean. An anti-social misfit that causes a groundswell of spleen wherever he goes."
-- Harry Middleton