Practice Test Geeks(MTC) Marine Technician Certification Practice Test
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Engine Performance & Tuning Flashcards

7 cards from real MTC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Engine Performance & Tuning flashcards as text

  1. When diagnosing a marine engine with an oxygen sensor, a consistently high voltage (0.8-0.9V) output indicates:

    Answer: A rich exhaust condition

    High O2 sensor voltage (close to 1V) indicates low oxygen content in the exhaust, which is characteristic of a rich air/fuel mixture.

  2. What does a technician check when performing a throttle position sensor (TPS) calibration on a marine EFI engine?

    Answer: That the TPS reads 0% at idle and 100% at WOT with correct voltage range

    TPS calibration verifies the sensor outputs the correct minimum voltage at closed throttle (0%) and maximum voltage at wide-open throttle (100%).

  3. A marine engine misfires only at high RPM under load. Ignition components test normal. Which fuel system issue should be suspected?

    Answer: Weak fuel pump unable to maintain pressure under high demand

    A weak fuel pump may maintain adequate pressure at idle but cannot supply sufficient volume at high RPM under load, causing lean misfires.

  4. On a marine diesel engine, what is the purpose of the injection advance mechanism?

    Answer: Advance injection timing as engine speed increases for optimum combustion

    The injection advance mechanism advances fuel injection timing as RPM increases to compensate for the shorter time available for ignition delay and combustion.

  5. A marine engine cooling system pressure test shows a 5 psi drop over 10 minutes. This indicates:

    Answer: An internal or external coolant leak

    A pressure drop during a cooling system pressure test indicates coolant is escaping through an internal leak (head gasket, crack) or an external leak (hose, fitting).

  6. When measuring piston ring end gap during engine overhaul, what is the consequence of installing rings with insufficient end gap?

    Answer: Ring ends butt together as rings expand from heat, causing ring breakage or scuffing

    Insufficient end gap causes ring ends to contact each other when the rings thermally expand, potentially breaking the rings or scoring the cylinder walls.

  7. Which parameter does a knock sensor monitor to allow the ECM to protect a marine engine?

    Answer: Crankshaft vibration frequencies associated with detonation

    A knock sensor detects specific high-frequency vibrations caused by detonation, signaling the ECM to retard ignition timing to prevent engine damage.