Alabama Boaters Engine Basics 2 — Questions and Answers
Question 1: What does the term 'cavitation' refer to in a boat engine system?
- Formation and collapse of vapor bubbles around the propeller (Correct answer)
- Buildup of carbon deposits in the carburetor
- Loss of fuel pressure in the fuel line
- Overheating of the engine block
Correct answer: Formation and collapse of vapor bubbles around the propeller
Cavitation occurs when low-pressure areas around the propeller cause water to vaporize, forming bubbles that collapse and can damage the propeller.
Question 2: Which type of cooling system circulates raw water directly from the lake or river through the engine?
- Closed cooling system
- Open (raw water) cooling system (Correct answer)
- Freshwater flush system
- Thermostat bypass system
Correct answer: Open (raw water) cooling system
An open raw-water cooling system draws water from the surrounding body of water directly through the engine and expels it with the exhaust.
Question 3: Before starting an inboard gasoline engine, you should run the blower for at least how long?
- 30 seconds
- 2 minutes
- 4 minutes (Correct answer)
- 10 minutes
Correct answer: 4 minutes
Running the blower for at least four minutes before starting an inboard engine ventilates the bilge and reduces the risk of gasoline vapor explosion.
Question 4: What is the primary purpose of a boat's thermostat in the cooling system?
- Regulate fuel flow to the carburetor
- Maintain engine operating temperature (Correct answer)
- Control oil pressure
- Monitor exhaust gas temperature
Correct answer: Maintain engine operating temperature
The thermostat regulates coolant flow to keep the engine within its optimal operating temperature range.
Question 5: What does a 'four-stroke' engine complete in two crankshaft revolutions?
- One intake and one exhaust stroke
- One complete power cycle (intake, compression, power, exhaust) (Correct answer)
- Two compression strokes
- Two power strokes
Correct answer: One complete power cycle (intake, compression, power, exhaust)
A four-stroke engine completes one full power cycle—intake, compression, power, and exhaust—in two full crankshaft revolutions.
Question 6: Which fuel system component is most important to inspect for cracks or leaks before each outing?
- Fuel tank vent
- Fuel filter
- Fuel primer bulb and hose (Correct answer)
- Carburetor float bowl
Correct answer: Fuel primer bulb and hose
The primer bulb and fuel hose are common failure points; cracks can allow fuel leakage and vapor buildup that poses a fire hazard.
Question 7: What indicates that a water-cooled outboard engine is circulating water properly after startup?
- Engine RPM increases steadily
- Water exits from the tell-tale (telltale) indicator (Correct answer)
- Oil pressure gauge reads high
- Throttle response is smooth
Correct answer: Water exits from the tell-tale (telltale) indicator
The tell-tale is a small stream of water expelled from the engine that confirms the water pump is functioning and the cooling system is operating.
Alabama Boaters Engine Basics 2
What does the term 'cavitation' refer to in a boat engine system?