Dan
I purchased my 1998 Johnson 115 from TIKI Marine off of Craigslist 4 years ago, they delivered to Lincoln called me to make sure everything was working fine. When you purchase any used motor you always take a risk, however I have run it for 4 years and not a single issue, I changed one carburator bowl because it leaked other that that no other issue.
I've owned Johnson's for 20 + years and they are great motors. Parts are simple to get and they are very easy to work on, I have the fast track trim now and my 1984 140 Johnson had the older trim, but I don't see any trim differances. I paid $ 3200 for my 115 4 years ago $1500 is a steal for a 1991 88...
I would buy it..
Joe