What's the best way to sell a good engine

My uncle had a good running poly, he tried to give it to me, I had no use for it, except maybe to use the steel crank.
He advertised it, offered it for free, no takers.
Then one day a guy drove down from OH, even though my uncle said take it, get it out of my way, free.
The guy gave him $200 for it, he needed it.
They are not a high demand engine, until you find that one buyer.