The one directly below the ignition switch looks more like a knob than a switch... this would be a tension control that keeps the throttle in place so that it doesn't wander due to engine or boat vibration.
The electrical plug below that is a tachometer hook up plug that consists of: signal sensor lead (gray wire), 12v lead when key is ON (purple wire - tach power supply), and ground (black wire). This 12v lead and ground availability can also be used for other purposes.