Outboards are strange things when it comes to buying second hand. There are some right dogs out there for silly money, and yet there are also some bargain minters aswell. I advise you to take some-one with you who knows what to look for, or buy from a reputable dealer with backup, (or buy brand new of course!). One thing outboards aren't is CHEAP! They are dear to buy, dear to run, dear to maintain and VERY dear when they go wrong, so be wary of what you spend your hard earned wedge on and try to get it right first time. It is an expensive lesson to learn the hard way! In the mean time try the link below for a company, in Fareham, who have given me nothing but good service for the last 9 years.
Regards
Jizm
http://www.outboardsdirect.co.uk/