Well join the club .
It's bloody one of life greatest mystery, (after how to keep a woman happy...... ) why something would work one day and it then refuse to do anything the next.
Back to your outboard, when you said no sparks, how bad is it?
1) you turn the key other than a 'click' sound nothing else happens.
2) you turn the key, the starter turns, but the engine won't turn over.
If it's 1) I would say, solenoid, worn starter motor (or brushes) or flat battery.
If it's 2), fuel not getting there, i.e., fuel pump, blockage or out of date fuel (not likely as you'd only used it the previous day) or you could have just flooded the spark plugs and nothing more.