An autozone universal compression tester is fine. Most of the outboards are 14mm spark plugs anywhere, which is what most older cars and trucks used, so normally the universal fit compression tester works. When you get into the 4 stroke stuff, some of those use smaller spark plug threads and you'd need the proper adapter (some are 12mm, some are 10mm)
https://lakeland.craigslist.org/bar/4784205259.html Saltwater use???
https://charlotte.craigslist.org/boa/4812386245.html
https://blacksburg.craigslist.org/boa/4810741885.html
https://memphis.craigslist.org/boa/4815758787.html
https://easternshore.craigslist.org/boa/4819017612.html
https://jonesboro.craigslist.org/boa/4800837114.html
https://cenla.craigslist.org/boa/4767402897.html
https://ventura.craigslist.org/boa/4799929350.html This one is a steal!!
https://pensacola.craigslist.org/boa/4791270342.html Hmmm...I may have to make a road trip to pick this one up!
Them are just a few. They're out there. Searching is easy. Take your pick, do you want 2 stroke or 4 stroke? 4 stroke holds it's value better, IMO. If you didn't like the 4 stroke, put it back on the market and it'll go. Them old 2 stroke motors are starting to die out slowly, some parts are being phased out and there's not much other choice but to buy another used motor or go with a new 4 stroke, or spend a LOT of money for one of them expensive ETEC's, which weigh a ton and cost a fortune...kind of defeating the purpose of 2 stroke, IMO.