Good condition is the operative word. What would you consider as good condition in an 83 with Twin Perkins and a 2004 with single Yanmar.
Lots of zen involved. "Condition" applies to the whole boat: hull, individual systems, etc. And there can be cases where an '83 boat might have had various systems already replaced/updated, whereas a 2004 boat might be on the verge of everything crapping out. Or there can also be cases where you'd prefer to replace crapped-out systems yourself...
Ideally, engines/gears/generators survey well (ideally done by a specialist in that brand), service is up to date per the maker's manual, oil and coolant analysis results are good, hoses are in good condition, bolt-ons (fuel coolers, gear oil coolers, heat exchangers, alternators, etc.) ditto...
Failures in some of that don't necessarily mean strike it off the list. Could become negotiating points for purchase price... and there's something to be said for getting the boat at a fair price and then bringing the engine(s) up to speed on your own dime.
You might like to have a go at this:
I think I'll be on this forum a lot in the next few years, so I decided to post early rather than lurk long. I was sitting at a picnic table near the lift bridge in Stillwater, MN two years ago when a trawler passed me on the St. Croix River. It piqued my interest for some reason (probably...
www.trawlerforum.com
And see post 15 in in that thread, links to additional discussions focused on costs, boat shopping, etc.
-Chris