The top one (white ring with black rubber disk) is a scupper. The rubber flap in the middle can swing out but not in. It is to let water out, and resist water from coming back in. They can be used for a self draining deck, but a little one like that is probably a drain from a storage compartment, or the well in front of the outboard engine.
The middle one (white knob) looks like a removable drain for a live bait-well or something.
Do you have the VDO gauges (the automotive style)? If so, you may have a depth gauge that shares the digital display with the clock. Press the Set and Mode buttons together for a couple seconds to switch between clock mode and depth mode.
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"Knot Easy" 2000 Horizon 240 Volvo 5.7GS /SX
tow: 2017 Honda PILOT EXL-AWD
prev. boats:
'87 Chaparral 198CXL 4.3 OMC Cobra
'69 Jetstar 16ft Ski Boat, 115hp Yamaha
'68 Aluminum Jon Boat, 3hp Sears
'64 Water Wings