Outboard engines: essential maintenance
At between 50 and 75 hours of use, or every three months, the following minimum tasks are appropriate for many outboard boat engines. Any other, more complicated, actions specified in the motor's manual may require special tools and an engineer's expertise.
Remove the spark plugs using a proper spark plug spanner, taking care not to damage the white ceramic insulator. If the engine is running as it should, the electrode will be light brown or grey in colour. Black or very white colouring indicates an engineer will need to diagnose faults.
Clean the plug or, preferably, replace it - particularly if it shows signs of breaking down. Check the gap with a feeler gauge and compare with the gap size indicated in the motor's manual, carefully adjusting as necessary.
Replace any leaking or worn components such as control cables.
The propeller may be secured to the shaft with a shear pin made of soft metal, designed to break if the propeller hits something. Spare pins should be available attached to the engine body. Check the condition of the pin. Ensure the outboard boat engine cannot start and then remove the propeller. Remove any debris from the shaft, check its condition and apply waterproof grease.
Drain the oil from the gear case. It should be brown but if watery or discoloured, professional repairs will be necessary. The manual will explain how to add oil to your particular motor's gear case. This usually involves pumping oil up into the drain hole to avoid air bubbles forming.
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 (for US), 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.