Alabama Boaters Engine Basics 4

Question 1

What does engine 'trim' refer to on a boat with an outboard or stern drive?

Accepted Answer

Changing the angle of the engine/drive unit relative to the transom

Answer

Trimming the engine adjusts the vertical angle of the lower unit, affecting the bow angle and performance of the boat.

Question 2

Which of the following is a sign that a spark plug may need replacement on a marine engine?

Accepted Answer

Engine misfires, rough idle, or difficulty starting

Answer

Misfiring, rough idling, and hard starting are common symptoms of worn or fouled spark plugs that are failing to ignite the fuel mixture reliably.

Question 3

What is the purpose of a shear pin or slip clutch hub on a propeller?

Accepted Answer

Protect the engine and gearcase by breaking or slipping when the prop strikes an object

Answer

The shear pin or slip hub absorbs the shock when the propeller hits an object, preventing damage from transferring to the gearcase and engine.

Question 4

What causes 'pre-ignition' in a marine gasoline engine?

Accepted Answer

Fuel igniting before the spark plug fires due to a hot spot in the combustion chamber

Answer

Pre-ignition occurs when the fuel-air mixture ignites prematurely from a hot spot such as a glowing carbon deposit before the spark plug fires.

Question 5

After striking a submerged object, what should you check on an outboard motor before restarting?

Accepted Answer

Propeller for damage and the shear pin or hub for failure

Answer

Striking an object can shear the prop's pin, bend blades, or damage the lower unit, so the propeller and its drive mechanism must be inspected before restarting.

(Alabama Boaters) Alabama Boaters Certification Practice Test

(Alabama Boaters) Alabama Boaters Certification Practice Test

Alabama Boaters Engine Basics 4