Without a strong, well-timed spark an engine won't start and run. This section covers how to test for spark and the main reasons why your may not be getting a good spark.

A very common reason that outboard motors run badly is from dirty in the carburettor(s). This can be from water or other contaminants in the fuel, perished fuel lines breaking up and putting debris into the fuel or varnish from fuel that has evaporated after the engine has been sitting for a long time.

There is a gasket that seals the cylinder head to the engine block to prevent the combustion gasses escaping and to keep the cooling water (and oil on a four stroke) out of the cylinders.

Outboards that have multiple carburettors need to the carburettors synchronised in order to run smoothly.