It is likely a bad bilge pump as there is no output of voltage if the pump fails. The output is controlled by the processor and not a fuse. You should have a Fault signal on the dash. Try rotating a pump or move the wires.
Also check the grounds on the terminal block as we feel you have a corroded terminal block on the transom as well and this prevents operation.
The Tachometer is usually the voltage regulator on the engine faulty in a Mercury. It is usually the Stator on an OMC Or Yamaha. The tachometer is only controlled by a signal from the engine and you probably have an engine problem.
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