Agree - generally smaller outboards give you the best profit potential, but maybe not as much as you think.
Take a 15 horse 2 stroke for example - popular motor.
A mid 80's to mid 90's model might sell, working properly, in the used market for 800-1000 bucks.
I picked up a 1991 model for 500 that was in pretty rough shape. 350 dollars in parts/paint etc and about 40 work hours later it was mechanically and cosmetically restored.
Now, I did that one for myself, but had I intended to re-sell it, even if I got a grand for it would have resulted in 150 bucks in my pocket for 40 hours of work.
That's just one example but from my experience I make 5 or 6 times that "hourly" simply doing repair work.
Way too many people want way too much money for that motor that has been sitting around for years "unused". You almost have to get it for nothing to make a repair/restore and resale worthwhile...