MST Cheat Sheet 2026

The 30 highest-yield MST facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. Why is regular maintenance of a boat’s engine cooling system important? → It prevents overheating and ensures the engine runs efficiently
2. What causes propeller ventilation on an outboard motor? → Surface air or exhaust gases being drawn into the spinning propeller
3. How do you perform a compression test on a marine engine? → By using a compression gauge to measure pressure in each cylinder
4. A technician drains and replaces engine coolant. Under EPA regulations, used coolant is classified as what type of waste if it contains high levels of lead? → Hazardous waste requiring proper disposal under RCRA
5. Why is it important to verify grounding in a marine electrical system? → Grounding ensures safe electrical current flow and prevents damage
6. Before applying a fiberglass patch, the damaged area should be ground to what profile? → A feathered 12:1 taper
7. What color is the standard fuel fill deck fitting on gasoline-powered boats to distinguish it from diesel? → Red
8. What is the role of boat maintenance in preventing corrosion? → To prevent corrosion by cleaning and using inhibitors
9. What is the first step in diagnosing engine issues in a marine engine? → Inspect the engine and assess the symptoms to identify potential causes
10. An inboard marine engine vibrates severely at all RPMs. The engine mounts appear good. What should the technician inspect next? → Propeller for damage or imbalance
11. What does a low vacuum reading (8–12 in. Hg) that is steady at idle indicate during an engine vacuum test on a marine engine? → Retarded ignition timing or late valve timing
12. What is the recommended action when a marine fuel system shows signs of phase-separated ethanol-blended fuel? → Drain and replace the fuel, then clean the tank and fuel system components
13. What is the first step in diagnosing electrical issues in a marine engine? → Check the battery for proper voltage
14. A NMEA 0183 sentence that begins with '$GPRMC' contains what information? → Recommended minimum specific GPS/transit data including time, position, speed, and course
15. A marine technician notices a customer's vessel has no placard stating 'Discharge of Oil Prohibited.' What is required? → Post a 5×8 inch placard in the machinery space
16. Why is a battery test necessary when troubleshooting electrical issues? → To ensure the battery is providing proper voltage and charge
17. What is the required sound signal for a power-driven vessel underway in restricted visibility, as specified in the COLREGS (Rule 35)? → One prolonged blast at intervals of not more than 2 minutes
18. What is the most common reason an outboard engine's tell-tale (water stream) has low or no flow but the engine temperature is normal? → A blocked or pinched tell-tale tube or fitting — not necessarily a pump problem
19. How do you diagnose overheating in a marine engine? → By checking the cooling system and ensuring no leaks or blockages
20. What is the maximum allowable AC voltage drop for shore power circuits on a marine vessel per ABYC standards? → 5%
21. What can cause an alternator failure in a marine engine? → Worn brushes or damaged rotor in the alternator
22. When replacing impeller blades in a raw-water pump, why should the impeller be installed with blade curvature facing the correct rotational direction? → Reversed curvature reduces pumping efficiency and causes rapid vane fatigue failure
23. What is the recommended torque sequence when reassembling a marine engine cylinder head? → Center bolts first, working outward in a crossing pattern
24. Which USCG regulation requires that all Type I, II, and III life jackets aboard recreational vessels be readily accessible and in good condition? → 33 CFR Part 175
25. When inspecting a through-hull fitting, a technician finds the seacock is stiff and difficult to operate. What is the correct action? → Apply marine grease and exercise the seacock; replace if operation does not improve
26. After a complete lower unit rebuild, the gearcase must be pressure-tested to check for leaks at what specification? → 3–5 psi held for several minutes with no pressure drop
27. What is the correct orientation for mounting an octahedral passive radar reflector? → In the 'catch-rain' position with one cavity facing up
28. How do you determine whether a marine engine's spark plugs are functioning correctly? → By testing spark output using a spark plug tester
29. A technician installs a new battery bank on a vessel. Under ABYC E-10, what is required to prevent accidental shorting of the battery terminals? → Insulated battery terminal covers or boots on all exposed terminals
30. Which safety precaution is most critical when working with MEKP catalyst? → Wear chemical splash goggles and nitrile gloves