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. Why is it important to verify grounding in a marine electrical system? → Grounding ensures safe electrical current flow and prevents damage
5. Before applying a fiberglass patch, the damaged area should be ground to what profile? → A feathered 12:1 taper
6. What color is the standard fuel fill deck fitting on gasoline-powered boats to distinguish it from diesel? → Red
7. What is the role of boat maintenance in preventing corrosion? → To prevent corrosion by cleaning and using inhibitors
8. What is the first step in diagnosing engine issues in a marine engine? → Inspect the engine and assess the symptoms to identify potential causes
9. What is the first step in diagnosing electrical issues in a marine engine? → Check the battery for proper voltage
10. A NMEA 0183 sentence that begins with '$GPRMC' contains what information? → Recommended minimum specific GPS/transit data including time, position, speed, and course
11. Why is a battery test necessary when troubleshooting electrical issues? → To ensure the battery is providing proper voltage and charge
12. 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
13. How do you diagnose overheating in a marine engine? → By checking the cooling system and ensuring no leaks or blockages
14. What can cause an alternator failure in a marine engine? → Worn brushes or damaged rotor in the alternator
15. 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
16. What is the correct orientation for mounting an octahedral passive radar reflector? → In the 'catch-rain' position with one cavity facing up
17. How do you determine whether a marine engine's spark plugs are functioning correctly? → By testing spark output using a spark plug tester
18. Which safety precaution is most critical when working with MEKP catalyst? → Wear chemical splash goggles and nitrile gloves
19. When fairing a hull repair, fairing compound should be applied in how many thin layers? → Multiple thin coats, allowing each to cure
20. What tool is used to cut out a damaged section of fiberglass hull cleanly for a patch repair? → Oscillating multi-tool or rotary cutter
21. Why are waste oil and fuel disposal systems important on a boat? → To safely dispose of harmful waste and prevent water contamination
22. What is the correct procedure to test a fuel system for leaks after a repair? → Pressurize with air to no more than 3 psi and check fittings with soapy water
23. What ABYC standard governs the installation of gasoline fuel systems on recreational boats? → ABYC H-24
24. How can you prevent damage to the boat's propeller? → By cleaning the propeller regularly and inspecting it for damage
25. What grit sandpaper is typically used for the final prep of gel coat before applying a color-matched gel coat patch? → 220–320 grit wet/dry
26. How does a 4-blade propeller generally differ from a 3-blade of the same pitch and diameter? → 4-blade provides better hole shot and reduced vibration but slightly lower top speed
27. Why must marine carburetors have a backfire flame arrestor? → To prevent engine backfires from igniting fuel vapors in the bilge
28. What is the maximum distance at which two VHF radios at sea level can typically communicate using line-of-sight propagation? → Approximately 20–25 nautical miles between two vessels depending on antenna height
29. What USCG-required channel must all recreational vessels monitor when operating in US waters? → VHF Channel 16
30. When removing an outboard propeller for service, what must be inspected before reinstallation? → The prop shaft splines, thrust washer, spacers, and prop seal for wear or damage