In the driver helm compartment, there are fuse boxes that are sort of water-resistant.
You will need to check these and the condition of the connectors at each gauge and device that is not functioning.
Fuel gauge on these boats is a common failure. There is a tiny fuse built into the sender that fails. Maybe yours has not failed yet. Again- check all your connections. Check for voltage at your devices (like bilge pump). They do fail; especially on 20 year old boats.
Tach- at the engine, at voltage regulator. There are 2 reg's. The gray wire is the tach sender wire. Another connector. If still not working; swap the tach wire to the other gray reg wire.