Re: 84 johnson 8hp carb replacement
You're going to need the correct carb for that outboard. It's similar to the 6hp of that year, not the 9.9 or any other outboard. Bolting a 6hp carb on won't work either, since there are other changes to make it an 8hp.
If you look hard enough and long enough, you'll find one. Start by contacting outboard wrecking yards, like
www.tcoutboard.com. You'll find one, it'll be expensive, and it will make your outboard run properly.
Watch ebay, if you're not in a hurry. They show up there from time to time.
The problem is that they made a lot fewer 8hp versions of that platform, so there are fewer used parts available.