MTC Advanced Diagnostics & Troubleshooting 2

Question 1

A four-stroke outboard engine cranks but will not fire. Spark is confirmed at all cylinders. What is the MOST logical next diagnostic step?

Accepted Answer

Verify fuel pressure and injector pulse signal

Answer

When spark is confirmed, the next step is to verify fuel delivery — pressure and injector operation — before moving to mechanical checks.

Question 2

Which symptom most strongly indicates a cracked engine block in a marine inboard?

Accepted Answer

Coolant level that drops without visible external leaks

Answer

A cracked block allows coolant to migrate internally without visible puddles, causing a steady unexplained coolant loss.

Question 3

A stern-drive unit vibrates heavily at speeds above 3,000 RPM but is smooth at idle. The most likely cause is:

Accepted Answer

A damaged or out-of-balance propeller

Answer

Propeller imbalance or damage creates centrifugal vibration that intensifies with RPM, not present at low speeds.

Question 4

When diagnosing an EFI marine engine with a lean misfire fault code, the technician should first inspect:

Accepted Answer

Mass air flow sensor output and vacuum lines for leaks

Answer

Vacuum leaks and MAF errors both introduce unmetered air, causing a lean condition before suspecting fuel-side components.

Question 5

A marine battery bank shows 12.6 V at rest but collapses to 9.8 V under starter load. This indicates:

Accepted Answer

Sulfated or failed battery cells with high internal resistance

Answer

Healthy batteries maintain near-resting voltage under load; severe voltage drop under cranking load is the classic sign of internal cell failure or sulfation.

(MTC) Marine Technician Certification Practice Test

(MTC) Marine Technician Certification Practice Test

MTC Advanced Diagnostics & Troubleshooting 2