Alabama Boaters Engine Basics 3 — Questions and Answers
Question 1: What is the function of a boat engine's water pump impeller?
- Pressurize the fuel delivery system
- Circulate cooling water through the engine (Correct answer)
- Lubricate the crankshaft bearings
- Regulate exhaust back-pressure
Correct answer: Circulate cooling water through the engine
The water pump impeller is a rubber vane that draws cooling water into the engine's cooling circuit to prevent overheating.
Question 2: When should the engine's oil level be checked on a boat?
- While the engine is running at idle
- Only at the start of the boating season
- Before each outing with the engine off and boat level (Correct answer)
- Immediately after shutting the engine down
Correct answer: Before each outing with the engine off and boat level
Oil level should be checked before each outing with the engine off and the boat on a level surface to get an accurate dipstick reading.
Question 3: What does a high engine temperature warning buzzer typically signal on an outboard motor?
- Low battery voltage
- Engine is overheating, possibly due to cooling water blockage (Correct answer)
- Fuel mixture is too rich
- Propeller is ventilating
Correct answer: Engine is overheating, possibly due to cooling water blockage
The overheating alarm indicates the cooling water flow is restricted, often by debris blocking the water intake, which can cause serious engine damage.
Question 4: Which propeller characteristic most directly affects a boat's top speed?
- Propeller color
- Number of blades only
- Propeller pitch (Correct answer)
- Hub diameter
Correct answer: Propeller pitch
Propeller pitch—the theoretical distance the prop advances per revolution—directly determines how fast a boat can travel at a given RPM.
Question 5: Why is it dangerous to run an outboard engine in a poorly ventilated area?
- The engine will stall from lack of oxygen
- Carbon monoxide exhaust can accumulate and cause fatal poisoning (Correct answer)
- Salt air will corrode the engine faster
- Engine oil will burn off quickly
Correct answer: Carbon monoxide exhaust can accumulate and cause fatal poisoning
Outboard engines produce carbon monoxide, a colorless, odorless gas that can reach lethal concentrations rapidly in enclosed or poorly ventilated spaces.
Question 6: What is the purpose of flushing an outboard motor with fresh water after use in saltwater?
- Increase engine horsepower
- Remove salt deposits that cause corrosion in cooling passages (Correct answer)
- Improve fuel economy
- Reset the engine's trim calibration
Correct answer: Remove salt deposits that cause corrosion in cooling passages
Salt crystals left in the cooling system can corrode internal passages and impair cooling; flushing with fresh water removes them.
Question 7: On a two-stroke engine, oil is typically introduced by:
- A separate oil sump below the crankcase
- Mixing with the fuel or an oil injection system (Correct answer)
- An external oil cooler attached to the hull
- The water-pump housing
Correct answer: Mixing with the fuel or an oil injection system
Two-stroke engines lubricate by mixing oil with the fuel, either pre-mixed in the tank or delivered through an oil injection pump.
Alabama Boaters Engine Basics 3
What is the function of a boat engine's water pump impeller?