? on a mercury tracer

The pressure specification is in the range of 30 to 45 PSI. The voltage at the pump with the key on, engine off should be 12 volts. With the engine running, the voltage should be about 9 volts at idle and 13 volts over 3500 RPM. Fuel pressure testing is hazardous, therefore take fire and fuel spray precautions. You also need a proper gauge for testiing. You can test the pressure at the valve on the hard fuel line on the injector supply lines.