Mercury 75 Service Manual page 54

WARNING
When testing or servicing the ignition system,
high voltage is present, be extremely cautious!
DO NOT TOUCH OR DISCONNECT any ignition
parts while engine is running, while key switch is
on, or while battery cables are connected.
CAUTION
Failure to comply with the following items may
result in damage to the ignition system.
1. DO NOT reverse battery cable connections.
The battery negative cable is (-) ground.
2. DO NOT "spark" battery terminals with bat-
tery cable connections to check polarity.
3. DO NOT disconnect battery cables while en-
gine is running.
4. DO NOT crank engine when switch box is not
grounded to engine.
A process of elimination must be used when check-
ing the ignition system without a Multi-Meter/DVA
Tester (91-99750) or a voltmeter (capable of measur-
ing 400 volts DC, or higher) and Direct Voltage Adap-
tor (91-89045), as the switch box and ignition coils
cannot be thoroughly checked with conventional test
equipment.
All other components can be tested with an ohmme-
ter. Before troubleshooting the ignition system, check
the following:
1. Make sure that electrical harness, ignition switch
and/or emergency stop switch are not the source
of the problem.
2. Check that plug-in connectors are fully engaged
and terminals are free of corrosion.
3. Make sure that wire connections are tight and
free of corrosion.
4. Check all electrical components, that are
grounded directly to engine, and all ground wires
to see that they are grounded to engine.
5. Check for disconnected wires, and short and
open circuits.
STATOR LOW AND HIGH SPEED OHM TEST
NOTE: Stator can be tested without removing from
engine.
1. Disconnect stator leads from switch box.
2A-16 - ELECTRICAL
2. Use an ohmmeter and perform the following
tests.
IMPORTANT: If stator is mounted on engine,
black stator lead must be grounded to power-
head when testing.
3 CYLINDER STATORS
75 MANUAL WITH 9 AMPERE STATOR
398-9873A20
USA-0D283222 THRU 0G227199
75/90 ELECTRIC WITH 16 AMPERE STATOR
398-9710A3
USA-0D283222 THRU 0G280043
BELGIUM-09793577 THRU 09879064
Test Leads
Between Blue Stator Lead
and Red Stator Lead
(Low Speed)
Between Red Stator Lead
and Engine Ground*
(Hi-Speed)
4 CYLINDER WITH 16 AMPERE STATOR
398-9710A31
USA-0D283222 THRU 0G301750
BELGIUM-09793577 THRU 09885527
Test Leads
Between Blue Stator Lead
and Blue/Wht Stator Lead
(Low Speed)
Between Red Stator Lead
and Red/White Stator Lead
(Hi-Speed)
3 CYLINDER STATORS
75 MANUAL WITH 9 AMPERE STATOR
398-9873A21
USA-0D227200 AND ABOVE
75/90 ELECTRIC WITH 14 AMPERE STATOR
398-9873A24
USA-0G280044 – 0G404505
BELGIUM-09879065 – 09916672
Test Leads
Between Blue Stator Lead
and Red Stator Lead
(Low Speed)
Between Red Stator Lead
and Engine Ground*
(Hi-Speed)
90-830234R3 DECEMBER 1997
Resistance Scale Reading
(OHMS) (x__________)
3.6-4.2
3600-4200
(R x 1000)
90-140
90-140
(R x 1)
Resistance Scale Reading
(OHMS) (x__________)
6.8 - 7.6
6800-7600
(R x 1000)
90-140
90-140
(R x 1)
Resistance Scale Reading
(OHMS) (x__________)
1.1-1.6
1100-1600
(R x 1000)
30-35
30-35
(R x 1)