1998 Johnson Evinrude "EC" 9.9 thru 30 HP 2-Cylinder Outboards Service Manual, Page 308Get this manual
Tachometer Circuit Tests9.9-30 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
1Set your peak-reading voltmeter to "POS" and "50"Check voltage at the batteryUse this reading as your refere nce for battery voltage2Use peak-reading voltmeter to check for battery voltage between the tachometer purple lead 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 circu its, engine fuse, key switchand the battery connections3With the engine NOT running and the key switch ONcheck 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 rectifier4With the engine running at 1000 RPM, check for voltage between the instrument harness gray lead and black lead at he dash If voltmeter shows volts, go to Step If voltmeter shows volts or higher, replace the tachometer5With the engine running at 1000 RPM, check for voltage at the engine terminal board gray connection If voltmeter shows volts, replace or repair the rectifier If voltmeter shows volts or higher, check the instrument harness and engine harness gray circuit for an open