Faria Beede Instruments Dress White 4" Tachometer - 7000 RPM Gas - All Outboards. 375" (85mm)Electronic tachometers work by counting pulses generated by the ingition system alternator tach signal generator or magnetic pickup sender. The tach is hooked up to +12VDC Ground and one of the signal sources listed above.By selecting the right tach and setting the switch on the back to the correct postion you let the tachometer know how many pulses are sent per each engine revolution.Benefits:Wide range of scales Multiple signal sources Rugged Reliable construction Specifications for Faria Beede Instruments Dress White 4" Tachometer: Manufacturer: Faria Beede Instruments Color: White Additional Features: Outboard Features of Faria Beede Instruments Dress White 4" Tachometer Perimeter-lighted black dial Stylish blue and white graphics Black aluminum bezel with burnished edge Flat glass lens American and metric scales and icons Package Contents: Faria Beede Instruments Dress White 4" Tachometer Faria Beede Instruments 33104: Dress White 4" Tachometer - 7000 RPM Gas - All Outboards