Mercury V6 175 Diagnostic Manual page 10

How to Use This Manual
• Never disconnect the battery while the engine is running. This can cause a voltage spike in the charging system that can
damage electronic components.
• Never separate the battery feed wire from the charging system while the engine is running.
• When charging the battery, disconnect it from the boat's electrical system. (This does not include low amperage battery
tenders or onboard chargers.)
• Ensure that all cable harnesses are connected solidly and that battery connections are thoroughly clean.
• Never connect or disconnect the wiring harness at the PCM when the ignition is switched ON.
• Before attempting any electric welding (MIG, TIG, stick), disconnect the battery leads and the PCM connectors. Ensure
that the ground clamp is as close to the work as possible.
• Steam cleaning or high pressure cleaning can cause many problems in the electrical system and should be avoided
whenever possible. If you are steam cleaning engines, do not direct the steam cleaning nozzle at EFI system components,
ignition system components or electrical connectors. If this happens, corrosion of the terminals or damage of components
can take place.
• Use only the test equipment specified in the diagnostic charts, since other test equipment may either give incorrect results
or damage good components.
• All voltage measurements using a voltmeter require a digital voltmeter with a rating of 10 megohms input impedance in
order to prevent damaging the circuitry of the PCM.
• Use a kV meter or appropriate spark tester for checking physical spark. Failure to do so can damage ignition system
components and endanger your safety.
• Do not allow spark plugs or wires to arc in the engine bay.
• Always relieve fuel system pressure prior to opening the fuel system. Safety glasses should be worn when working on the
fuel system.
Page 1A-4 © 2018 Mercury Marine 90-8M0146617 eng JULY 2018