With internet now widely accessible worldwide it has become common to find and order used outboards from specialist shops with just a few clicks of a mouse. Such purchases prove to be safe and money/time saving and the outboards are professionally maintained/tested before being sold and come with different kinds of warranty.
If you don't want to risk buying a used outboard from a private seller, I would recommend visiting such well established specialists as hardcoremarine.com (for US), casse-marine.com (for France and Mediterranean), outboards-direct.co.uk or avondale-marine.com (worldwide).
If, however, you cannot find an outboard you need from a specialist and are planning to buy one from a private seller, you need to be extra careful and inspect it inside and out before purchasing. If you are unsure, seek advise from an engineer, as buying privately offers no guarantees and could result in unexpected expenditures rectifying technical faults.
Damage to any used outboard motors you are viewing may be revealed by close inspection. Expect superficial scratches to paintwork but if there are signs of an impact, don’t buy it.
The most vulnerable parts are those that come into contact with underwater obstacles such as rocks and submerged supermarket trolleys. The propeller should be smooth and regular in shape. View it from many different angles to check. The skeg is the pointed part that extends below the propeller to protect it to some extent. This can show signs of collision damage. If the skeg and/or the propeller is bent or damaged there could be consequent, more serious damage to the propeller shaft and other internal components.
When looking at used outboard motors, remove the engine cover and inspect the parts carefully. Look for leaks of fuel, oil or water indicating damaged seals or gaskets. Check for corrosion caused by such leaks. Electrical connections and components should be tight and in good condition.
A two stroke motor will give off some smoke in its exhaust, but if there are still clouds of it coming from a well warmed up motor, there could be problems - although it may be that too much oil has been added to the fuel. Smoke from the exhaust of a warmed up four stroke engine is more serious as it should burn fuel cleanly.
Remove and check the spark plugs for excessive deposits which could indicate adjustments or repairs are necessary. Defects must be checked by an engineer if you still want to buy showing any problems.