You are right of course there are some brilliant bargains in the older engines. My current 15hp is a "holy grail" type but in truth I've had amazing service from older much less valuable ones.
For several years until we sold the outfit this old model (1985 or so) Mariner 20hp powered our 12ft Bonwitco fast fishing boat about the West coat on holidays with only oars for backup (only ever needed for rowing into shallows). Here seen powering away from Loch Caolisport towards the sound of Jura.
It was as smooth, reliable and easy to start as any newer engine we've