After the motor is stopped, allow any water to drain out before lifting the outboard off the boat or tilting up. Fuel should be drained from the carburettor by turning off the fuel supply before stopping the outboard boat engine and allowing the fuel to be used up as the motor comes to a stop. This is safer than draining the carburettor by unscrewing its drain plug and collecting the fuel in a rag which is then a fire hazard.
If the motor has been used at sea, flush the cooling system with fresh water to remove corrosive salt deposit. Mount the outboard boat engine securely and safely so that it can be run in a large, strong container of fresh water. While the motor is running, check and lubricate the controls if necessary and inspect for any leaks of water or fuel. Tighten bolts/screws/clamps if leaks are found – or replace the worn parts.
If the motor is left on the boat, it should be tilted up out of the water. Use a lockable security clamp to prevent theft. When transporting the motor, keep the head higher than the propeller and follow any instructions on it concerning the side on which to lay it down.
With the outboard boat engine secured so it won’t fall on you:
Check wiring connections, cleaning and tightening where necessary
Spray with water dispersant anti-corrosion spray
Check fuel filters, removing any dirt or water
Check fuel line and bulb for deterioration and leaks
Lubricate moving parts such as the tilt mechanism and steering pivot which may need grease inserted into a grease point On a four stroke engine top up the engine oil if necessary
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.