Re: 1978 85HP Evinrude V4 Tach.
A universal tachometer with a 6p setting is required.
Positive 12 Volt DC may be supplied from the remote control purple wire.
Negative ground may be supplied from the small M post on the ignition switch wiring.
The signal wire is a gray wire in the main harness. It runs from the third connector on the engine terminal block to the remote control.
A standard side mount remote is prewired for a tachometer with an amphenol plug below the ignition switch; it is similar to the one shown here:
http://www.maxrules.com/graphics/omc_pics/REMCONTBOX.jpg.
When wiring the tachometer, have the battery disconnected. Any voltage riding the gray wire will instantly destroy the rectifier, which is required for operation of the tachometer.
