MerCruiser 305 CID (5.0L) Service Manual page 611

FUEL INJECTION SYSTEM TROUBLESHOOTING
Lack of Power, Sluggish or Spongy Symptom (Continued)
Step
11
12
13
14
15
16
17
18
Index
Page 5F-10
Action
1. Check ignition coil for cracks or carbon
tracking.
Were cracks or carbon tracks found?
1. Check for intermittent opens or short to
grounds in the ECT sensor, MAP sensor
and TP sensor circuits. Also check or
throttle linkage sticking, binding or worn.
2. An intermittent failure may not store a DTC.
Was a problem found?
1. Check ECM grounds for being clean, tight
and in their proper locations.
Were ECM grounds
improperly connected?
1. Check diagnostic test CKT 451 for being
shorted to ground. This will cause the rpm
to be lowered.
Was a problem found?
1. Check for proper alternator voltage output.
Is voltage between 11 - 16 volts?
1. Check for the following Engine Mechanical
problems:
• Low compression.
• Leaking cylinder head gaskets.
• Worn or incorrect camshaft.
• Proper valve timing/valve train problem.
• Restricted exhaust system.
Was a problem found?
1. Check for excessive resistance on the bot-
tom of the boat such as dirt, barnacles, etc.
2. Check for proper propeller size and pitch
for that application.
Was a problem found?
1. Review all diagnostic procedures within
this table.
2. When all procedures have been completed
and no malfunctions are found, review/in-
spect the following:
• Visual/physical inspection.
• Scan tool data.
• All connections within a suspected circuit
and/or system.
Was a problem found?
dirty, loose or
SERVICE MANUAL NUMBER 24
Yes No
PROCEED TO
Step 12
Step 13
Step 14
OBD
Step 15
Step 16
Step 17
Step 18
OBD
Contact
MerCruiser
Customer
OBD Service
90-861327--1 OCTOBER 1999