單項選擇題If the back clearance of a piston ring is excessive,（）

A.compression pressure in the cylinder will be higher
B.carbon will accumulate behind the ring
C.combustion gases will penetrate beneath the ring land
D.piston side thrust will be increased


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2.單項選擇題If a crankcase explosion has occurred in a diesel engine, and the crankcase remains intact, which of following precautions should be observed?（）

A.The cylinder indicator cocks should be opened
B.The sump lube oil scavenge pump should be secured immediately
C.The explosion relief valves should be manually opened
D.The crankcase should remain unopened until the engine has cooled

3.單項選擇題A sudden power loss from a turbocharged and after-cooled diesel engine is an indication of a/an（）

A.turbocharger malfunction or failure
B.crankcase exhauster overload
C.overload on the intercooler
D.obstruction in the engine cylinders

4.單項選擇題If a diesel engine has been stopped because of piston seizure due to severe overheating, the crankcase（）

A.inspection covers should not be opened until the engine has cooled
B.ventilation system should be continued in operation for one hour for cooling
C.scavenge pump should be immediately secured to prevent loss of lube oil
D.explosion covers should be opened slightly to provide extra ventilation

5.單項選擇題The desirable properties of a marine fuel oil should include（）

A.high flash point and high viscosity
B.low flash point and high viscosity
C.low heating value and high sulphur content
D.high heating value and low sulphur content