Re: Qd-17 10hp
Which parts? Basic tune-up stuff is available right here on i-boats, at your local Johnrude dealer, local NAPA, etc. That would include coils, points, condensers, carb kit, waterpump impeller, lower unit seals, etc.
As for gas tanks - poke around your local marinas. Most have a few tucked away somewhere, even if they don't know it. Showing up at coffee time with a box of donuts may help get you in their good graces enough to allow you to peruse the junk piles, back sheds, lofts, etc.
Also, try eBay, Craigslist, AOMCI.org, etc.