Vibration - Drive Engaged
Problem / Symptom
Cause
Action
Rough at All Speeds
Engine and propeller shaft mis-
aligned
See your authorized Yanmar deal-
er or distributor
Leaking cylinder head gasket
Bent propeller shaft
Rough at Higher Speeds
Bent propeller
See your authorized Yanmar deal-
er or distributor
Slipping clutch / clutch dog
Incorrect injection pressure
Injection timing is incorrect
Engine Knocks
Problem / Symptom
Cause
Action
Excess Fuel Injected
Defective fuel injector
See your authorized Yanmar dealer
or distributor
High fuel injection pressure
Noise Changes with Engine Load
Incorrect or poor quality fuel
Drain and refill tank with proper fuel
Worn crankshaft / bearings
See your authorized Yanmar dealer
or distributor
Broken piston / rings
Low Power Output
Problem / Symptom
Cause
Action
Miscellaneous
Clogged air filter
Replace air filter
Leaking cylinder head gasket
See your authorized Yanmar deal-
er or distributor
Damaged turbocharger
Incorrect propeller
Excessive exhaust back pres-
sure
Fuel
Plugged fuel filter(s)
Replace as necessary
Faulty fuel supply pump
See your authorized Yanmar deal-
er or distributor
Low Fuel Injection Pressure
Defective fuel pressure regula-
tor / sensor
See your authorized Yanmar deal-
er or distributor
Worn high-pressure fuel pump
Injection timing is incorrect
Low RPM at Wide Open Throttle
Propeller pitch too great
See your authorized Yanmar deal-
er or distributor
Engine overheated
Damaged turbocharger
TROUBLESHOOTING
62
BY Series Operation Manual
© 2008 Yanmar Marine International