Well, I would go with what the others have said. Craigslist is your friend and perhaps look around at some local repair shops. They have some left over from repairs or whatnot and at times have them for sale in their shop.
Mine is an 8.0 Johnson longshaft, and one day will tell you a very funny story about that
Its, an 86 I think and runs great. More than enough power and has a generator built in as well. Came with the boat when I bought it, and I believe it was purchased new with the boat and has been with her ever since.
They are out there you just have to look hard and dig deep. People hold out on them as I have discovered but with some prodding they might let one go

There seems to be the four stroke vs two issue , people I know are hugging the two strokes with new regulations coming along requiring four strokes.
Boat is a 1980 25 in good condition. The only issue I am dealing with is finding a motor since the owner would not part with his. He had a 9.9 Johnson 2 cycle which you can no longer buy. I found some used one's for $600-$700 but they are 1977 or do I go for a 4 cycle which is a weight issue unless I go down in hp. Thoughts?