Just brought my new to me 312 Fastech home for the first time. Going through the cabin I found a key (not ignition) that I can't seem to figure out what it locks. Is there anything on this boat that requires a key other then the ignition?

Sliding cabin door?

No it's not the cabin door.

On my FASTech there is a panel under steering column/wheel.

Is it round?

Yes

Did you buy the one from the classifieds here?

Round like a vending machine key?

Could be the access panel under the throttles/shift cables?

No, bought it from a local guy here in Michigan. It's a 2000with 68 hrs in perfect condition. Still has the new boat smell in the cabin.

Yes the key is round like a vending machine key.

The 312 panel that is under the dash has a knob on it and not the round key. The round key is used to access the back side of the circuit breaker panel. See attached pic with red circles. Enjoy your new ride!