Step Action Yes No
1
Was the Visual/Physical Check completed?
Go to step 2.
Go to the Visual/
Physical Check.
2 Did the onboard diagnostic (OBD) system check complete? Go to step 3.
Connect the CDS G3
service tool and scan for
faults.
3
Check the operator's driving habits.
• Are excessively heavy loads being carried?
• Is the operator accelerating too much or too often?
Was a problem found?
System normal. Go to step 4.
4
Check all fuel lines and connections for leaks.
Was a problem found?
Repair or replace.
Retest the system.
Go to step 5.
5
• Check for excessive resistance on the bottom of the boat
such as dirt or barnacles.
• Check for a damaged propeller.
• Check for proper propeller size and pitch for that
application.
Was a problem found?
• Clean the boat bottom.
• Repair or replace the
propeller.
Go to step 6.
6
Check the flame arrestor for dirt, damage, or any restriction.
Was a problem found?
Clean or replace the flame
arrestor.
Go to step 7.
7
• Check for contaminated fuel.
• Check fuel filters and the water‑separating fuel filter.
• Check for poor fuel quality and improper octane rating.
Was a problem found?
Use known good fuel.
Replace the fuel filters.
Go to step 8.
8
Check for proper fuel pressure while the condition exists.
Was a problem found?
Go to Chart T3.
Go to step 9.
9
Check the fuel injectors.
Was a problem found?
Repair or replace the faulty
injector.
Go to step 10.
10
Check for adequate spark at all of the spark plugs.
Was adequate spark present?
Go to step 11.
Go to Chart T4.
11
Remove the spark plugs and check them for moisture, cracks,
wear, improper gap, burned electrodes, or heavy deposits.
NOTE: If the spark plugs are fouled with gas or oil, the cause of
the fouling must be determined before replacing the spark
plugs.
Was a problem found?
Replace the spark plugs. Go to step 12.
12
Check the vacuum hoses for splits, kinks, and improper
connections.
Was a problem found?
Repair or replace the vacuum
hoses.
Go to step 13.
13
Check engine compression.
Was a problem found?
For repair, refer to Section 3 ‑
Engine Mechanical.
Go to step 14.
14
Check the exhaust system for possible restrictions. Inspect the
exhaust system for damaged or collapsed pipes.
Was a problem found?
Repair or replace. Go to step 15.
15
Review all of the procedures in this table. If all procedures have been completed and no problem found, inspect the
following:
• CDS G3 scan tool data
NOTE: If there are any active onboard diagnostics ‑ marine (OBD‑M) faults, refer to the
PCM 112 Service Manual
.
• All of the electrical connections within a suspect circuit or system
Chart S8: Dieseling or Run‑On
Definition: Engine continues to operate roughly after the key is moved to the off position.
If the engine operates smoothly, first check the ignition switch and adjustment.
Troubleshooting
90-8M0099748 eng DECEMBER 2015 © 2016 Mercury Marine Page 1D-17
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