MTC Engine Performance & Tuning 2

Question 1

What does a high vacuum reading on a manifold vacuum gauge (18-22 in. Hg at idle) typically indicate?

Accepted Answer

Normal engine operation

Answer

Rich air/fuel mixture

Answer

Retarded ignition timing

Answer

Leaking intake manifold gasket

Question 2

When tuning a carbureted marine engine, which jet size change would richen the mixture at wide-open throttle?

Accepted Answer

Larger main jet

Answer

Smaller main jet

Answer

Smaller pilot jet

Answer

Larger needle jet

Question 3

A marine engine exhibits detonation (knock) under load. Which of the following is the MOST likely cause?

Accepted Answer

Ignition timing too advanced

Answer

Fuel octane too high

Answer

Ignition timing too retarded

Answer

Rich air/fuel mixture

Question 4

Which tool is used to measure crankshaft end play during engine assembly?

Accepted Answer

Dial indicator

Answer

Micrometer

Answer

Feeler gauge

Answer

Plastigage

Question 5

On a four-stroke marine engine, what stroke follows the compression stroke?

Accepted Answer

Power stroke

Answer

Intake stroke

Answer

Exhaust stroke

Answer

Overlap stroke

Question 6

What is the purpose of an intercooler on a turbocharged marine engine?

Accepted Answer

Cool compressed intake air before it enters the engine

Answer

Cool engine coolant before the thermostat

Answer

Reduce exhaust gas temperature

Answer

Cool engine oil after the oil cooler

Question 7

A marine technician notices black smoke from the exhaust at full throttle. What does this typically indicate?

Accepted Answer

Too rich an air/fuel mixture

Answer

Too lean a mixture

Answer

Water in the fuel

Answer

Worn piston rings