Practice Test Geeks(MST) Marine Service Technician Practice Test
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Marine Engine Diagnostics & Repair Flashcards

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

Read the first 7 Marine Engine Diagnostics & Repair flashcards as text

  1. During valve adjustment on a marine engine, the technician finds one exhaust valve has zero clearance. What symptom would this most likely cause?

    Answer: Hard starting due to low compression in that cylinder

    Zero valve clearance on an exhaust valve can cause it to remain slightly open, reducing compression in that cylinder and making the engine hard to start.

  2. A marine technician finds water in the engine oil, giving it a milky appearance. The cooling system pressure test holds. What is the next component to inspect?

    Answer: Oil cooler for internal leaks

    If the cooling system holds pressure externally, an internal oil cooler leak allows coolant to mix with oil without showing external loss, making it the next logical suspect.

  3. What is the correct method to set ignition timing on a marine engine equipped with a mechanical distributor?

    Answer: Connect a timing light to cylinder #1 and align the timing mark at idle with vacuum advance disconnected

    Base ignition timing is set at idle with vacuum advance hose disconnected and plugged, aligning the crankshaft timing mark with the specified degree mark using a timing light on cylinder #1.

  4. A two-stroke outboard fouls spark plugs repeatedly. The engine smokes heavily and has poor performance. What is the most likely cause?

    Answer: Too rich a fuel-to-oil mixture or faulty oil injection pump

    Repeated plug fouling with heavy smoke in a two-stroke indicates an excessively rich oil/fuel ratio, often from a faulty oil injection pump delivering too much oil.

  5. When pressure-testing a marine raw water cooling system, where should the pressure cap adapter be installed?

    Answer: At the raw water pump inlet

    The pressure test adapter is installed at the raw water pump inlet to pressurize the entire raw water circuit from the point of entry and detect leaks throughout the system.

  6. A marine engine has a strong fuel smell in the bilge with no visible fuel leaks. What is the most likely source?

    Answer: Carburetor needle and seat not sealing

    A carburetor needle and seat that fails to seal allows fuel to overflow and drip into the engine compartment/bilge, producing a strong fuel odor without obvious external fuel lines leaking.

  7. Which symptom indicates a marine engine's timing chain or belt has jumped one tooth?

    Answer: Loss of power with backfire through intake or exhaust at specific RPM

    A jumped timing chain shifts cam timing, causing valve events to occur out of synchronization with piston position, resulting in power loss and backfiring at specific RPM ranges.