MTC Engine Performance & Tuning 3

Question 1

When performing a cylinder leak-down test on a marine engine, what does a reading of 25% leakage indicate?

Accepted Answer

Excessive leakage requiring investigation

Answer

Excellent cylinder sealing

Answer

Normal wear within spec

Answer

The test is inconclusive

Question 2

What is the correct procedure for setting valve clearance on an overhead cam marine engine?

Accepted Answer

Set clearance with the cam lobe pointing away from the follower

Answer

Set clearance with the engine at operating temperature only

Answer

Set clearance with the cam lobe pointing directly at the follower

Answer

Set clearance only when cylinder is on overlap

Question 3

A two-stroke marine engine produces excessive power loss. Air-cooled reeds are found worn and not sealing. What is the likely result of this condition?

Accepted Answer

Loss of crankcase compression and poor scavenging

Answer

Increased fuel efficiency

Answer

Excessive oil consumption

Answer

Overheating of the cylinder head

Question 4

Which of the following best describes volumetric efficiency in a marine engine?

Accepted Answer

The ratio of actual air/fuel mixture drawn in vs. theoretical cylinder volume

Answer

The ratio of brake horsepower to indicated horsepower

Answer

The efficiency of fuel combustion in the cylinder

Answer

The ratio of torque to engine displacement

Question 5

On a marine engine with electronic fuel injection, a MAP sensor reading lower than actual manifold pressure would cause the ECM to:

Accepted Answer

Lean the fuel mixture

Answer

Enrich the fuel mixture

Answer

Advance ignition timing

Answer

Increase idle speed

Question 6

What is the primary function of a harmonic balancer on a marine engine crankshaft?

Accepted Answer

Dampen torsional vibration in the crankshaft

Answer

Balance the weight of the flywheel

Answer

Drive the camshaft timing belt

Answer

Provide a mounting point for the timing marks

Question 7

A marine technician observes that engine oil pressure drops significantly at operating temperature but is normal when cold. The MOST likely cause is:

Accepted Answer

Worn main and rod bearings

Answer

Faulty oil pressure sending unit

Answer

Clogged oil filter

Answer

Defective oil pump relief valve stuck closed