Marine Technician Engine Systems Flashcards

What is the purpose of a marine engine's raw water strainer?

Answer: To filter debris before water enters the cooling system

The raw water strainer removes debris and particulates from seawater before it reaches the impeller and cooling circuit.

A four-stroke inboard diesel engine fires on which stroke?

Answer: Power stroke

Combustion occurs at the top of the compression stroke and drives the piston down during the power (expansion) stroke.

Which component in a marine diesel injection system controls the precise timing and quantity of fuel delivery?

Answer: Injection pump

The injection pump meters and pressurizes fuel, delivering it to injectors at the correct timing and quantity for each cylinder.

When inspecting a flexible engine mount, which condition warrants immediate replacement?

Answer: Rubber bonded to metal showing cracks or separation

Cracks or separation in the rubber-to-metal bond indicate the mount has failed its isolating function and can allow damaging vibration or engine misalignment.

What does a high exhaust back pressure reading indicate on a marine engine?

Answer: Restriction in the exhaust system

Elevated back pressure indicates a blockage or restriction—such as a clogged muffler or collapsed hose—that impedes exhaust gas flow.

A marine technician notices white smoke from a diesel engine at startup that clears after warm-up. What is the most likely cause?

Answer: Normal combustion of condensed moisture and unburned fuel during cold start

White smoke on a cold diesel start is typically condensed water vapor and lightly unburned fuel that dissipates once the engine reaches operating temperature.

What is the function of the thermostat in a freshwater-cooled marine engine?

Answer: Maintain consistent engine operating temperature by controlling coolant circulation

The thermostat restricts coolant flow until the engine reaches its designed operating temperature, then opens to allow full circulation through the heat exchanger.