Mystery toggle switch on SO 36.2 ignition panel

[Sea Horse]

I inherited a 1997 SO 36.2. I have learned a lot about it but can’t figure out what this little black toggle switch on the ignition panel is for. It’s about an inch long and to the left of and below the key and start button. Any ideas? 

[Charlie-Bravo]

Some boats have a fuel gauge switch, with the engine on , hold the switch on and the fuel gauge then reads the fuel level.
Could also be many other things, but that’s what is on my panel.
CB

[tomina]

I have a 2001 SO 40. It’s the fuel level switch. Hold down and it shows the level in the tank. Mine reads full or almost full until the tank is about half then drops like a stone to show the true level and seems to read pretty accurately from then on.

[Sea Horse]

Thank you everyone!