1997 Johnson/Evinrude EU 25, 35 HP 3-Cylinder outboards Service Manual, Page 245Get this manual
Tachometer Circuit Tests Perform the following tests if the tachometer does not operate
INote The tachometer circuit is driven by the stator outputBefore proceeding, check condition of the
stator following Stator Resistance Tests, this section
Important
Verify that all engine and boat wiring and connectors are in good condition
INote Do not energize the primer while performing these tests1Set your peak-reading voltmeter to "POS" and "50"Check voltage at the batteryUse this reading as your reference for battery voltage2Use peak-reading voltmeter to check for battery voltage between the tachometer purple lead and black lead at the dash with the engine NOT running and the key switch ON If the voltmeter shows battery voltage, go to Step If the voltmeter shows less than battery voltage, check the purple, purplered, and black circuits, engine fuse, key switch, and the battery connections3With the engine NOT running and the key switch ON, check for battery voltage between the instrument harness gray lead and black lead at the dash If voltmeter shows volts, go to Step If voltmeter shows any voltage, replace the rectifierregulator4With the engine running at 1000 RPM, check for voltage between the instrument harness gray lead and black lead at the dash If voltmeter shows volts, go to Step If voltmeter shows more than volts, replace the tachometer5Disconnect the purple lead connector between engine harness and rectifierregulatorWith the engine NOT running and the key switch ON, check for battery voltage at the engine harness purple lead If voltmeter shows battery voltage, replace the rectifierregulator If voltmeter shows NO battery voltage, check instrument harness and engine harness purple and purplered circuits, engine fuse and key switch