Page 30 - REPOWER REFERENCE GUIDE (2020)

Engine Failure Diagnosis

Steps to Follow
IMPORTANT: If the engine is suspected as the problem, always do a compression check.
Remember the customer input is key to diagnosing the cause of any problems with the boat engine, including engine failure.
Be certain to obtain and evaluate the following customer‑supplied information.
• Customer experience at the time of failure
• How the customer normally operates the boat
• Engine RPM at wide‑open throttle (WOT)
• Boat speed
• Maintenance records
Other key areas to investigate include.
• Exhaust components (engine and boat)
• Ignition system
• Fuel system (engine and boat)
• Electrical system (engine and boat)
• Cooling system (engine and boat)
• Engine, including:
External condition
Cylinder compression and leak down
Internal inspection
• Boat condition (example: bottom growth)
• Condition of the sterndrive, inboard running gear, and propellers
Causes for Marine Engine Failure

IMPORTANT: A proper repair follows up with an inspection of the key components to answer why the failure happened.
• Lack of lubrication
• Overload or fatigue
• Overheating
• Water ingestion or hydro‑lock
• Detonation or preignition

Bearing failure
a - Lack of oil (overlay partially
worn off)
b - Dirt embedded in bearing
material
a b 68056

Page 3A-4 © 2019 Mercury Marine 90-8M0149179 eng NOVEMBER 2018