Page 29 - REPOWER REFERENCE GUIDE (2020)

Engine Failure Diagnosis

• In the case above a noisy engine was brought in. The damaged plugs were removed to find a melted piston. Changing the
longblock did nothing to fix the cause of the issue, but it addressed the symptom until the next piston melted. It wasn't until
after great expense and much stress that a proper diagnosis of dirty injectors was found to be the root cause. The fuel
injectors were not properly serviced, that resulted in unstable combustion, and that led to melted pistons.
• If the failure is warrantable, then the factory has its own root cause analysis to perform. The warranty process is structured
to facilitate a root cause analysis, timely payments, and maximize quality.
• A proper repair to find the root cause and fix the issues is much like being a detective to solving the case of the noisy
engine. It's important to continue to follow the clues left behind until the culprit is found. Otherwise a customer is left
unhappy perhaps to leave boating behind as something they used to do. If boating is not a pleasure this puts everyone's
business at risk due to customers potentially walking away from boating: along with their friends and family.
• The following sections offer suggested steps to follow for a root cause analysis, and examples of component failure
analysis to aid with a proper diagnosis.
• With every major repair, determine why the failure occurred.

Fuel injectors
a - FAIR—but weak
b - BAD—split spray pattern
a b c d e f c - BAD—split spray pattern
d - BAD—jetting on left side
e - GOOD
f - BAD—feathering at the top of the
spray

68053

27651
Preignition damage

23037

Detonation damage

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