Mercury V6 175 Diagnostic Manual page 206

Accessories
Engine Off Test
Record the voltage of the house
battery.
5. NOTE: The voltage should be
11.5–12.5 V. If voltage is lower
than 11.5 V, charge the battery.
Record the voltage of the engine
battery.
6. NOTE: The voltage should be
11.5–12.5 V. If voltage is lower
than 11.5 V, charge the battery.
Check for continuity from all
isolator posts to common boat
ground.
7.
NOTE: Each "output" post should
read the respective battery voltage
and the "input" should read 0.
If voltage is found on the input
8.
stud, replace the isolator.
If no voltage is found on the input
9. stud, proceed to Engine Key On
Test.
Page 5C-10
Engine Key On Test
Record the voltage of the engine
5.
battery.
Record the voltage of the house
6.
battery.
Trim the engine down and stall the
trim in the down position.
7.
Verify that only the engine battery
has voltage drop.
If voltage drops on both batteries
8.
replace the isolator.
If voltage drops on the engine
9. battery only, proceed to Engine
Running Test.
© 2018 Mercury Marine
Engine Running Test
Start the engine and allow it to run at idle
5.
speed.
6. Record the voltage of the engine battery.
Record the voltage of the house battery.
NOTE: Voltages should be slightly above
what was noted in the Engine Key On
. If not, check the voltage on the
Test
7.
input stud. The input stud voltage should
be 13.5 V or higher. If voltage does not
make it "through" the isolator, replace the
isolator.
Place the engine in throttle only mode
8. and increase the engine speed to 1000
RPM.
9. Record the voltage of the engine battery.
Record the voltage of the house battery.
NOTE: Voltage at both the engine and
house batteries should be higher than
what was recorded in the idle test. If not,
10.
check the voltage on the input stud. The
input stud voltage should be 14.5 V ±
0.5V. If voltage is not making it "through"
the isolator, replace the isolator.
90-8M0146617 eng JULY 2018