Sparks start at Magneto which is found under flywheel...so first step is to
remove flywheel (sometimes routine sometimes not) When flywheel has been
removed, clean (polish) and gap ignition points...if that produces a bright
blue spark at spark plug you may be good to go. If still no spark you may
want to check all connections for looseness or corrosion.
Sometimes all that is needed is a tuneup, however if an inspection reveals
a need for parts such as coils note the brand and model of magneto so
the correct parts can be sought. Many outboard makers sourced components
such as magnetos and carburetors from vendors...sometimes several different
vendors supplied parts at different times for same motor.
When and if you find you need specific parts there are several ways to go
to find them. For the present see what lurks under flywheel