If you can hear the starter solenoid click when you turn the key or press the start button it means that the key switch is working and has power to it. You can also be reasonably certain the solenoid itself is working, although making a clicking sound is not a 100% guarantee of that.
PHOTO Dangar Marine Boat Guide
The starter motor spins but doesn't turn the flywheel
Open ›The starter spins or catches only briefly without turning the engine, which can look like a flat battery. I show how the Bendix gear works and how to clean and lubricate a gummed-up shaft.
The starter motor doesn't spin but the solenoid clicks
Open ›This topic covers the situation where you turn the key on your boat and the starter motor doesn't spin but you can hear the solenoid clicking.