Marine Technician Fuel & Cooling Systems Flashcards
7 cards from real MTC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Marine Technician Fuel & Cooling Systems flashcards as text
A marine technician notices white powdery deposits around coolant hose clamps on a raw-water-cooled engine. This MOST likely indicates:
Answer: Raw water seeping past a loose clamp connection
White mineral deposits (scale) around hose clamps signal raw water seepage; raw water evaporates and leaves mineral residue, unlike antifreeze which leaves a sticky colored stain.
What is the purpose of a fuel/water separator in a marine diesel fuel system?
Answer: To remove entrained water before it reaches injection components, preventing corrosion and poor combustion
Water in diesel fuel damages injection pumps and injectors; a fuel/water separator coalesces and collects water in a bowl that must be drained regularly.
On a stern-drive engine, raw water enters the cooling system through the drive unit lower unit and exits via the exhaust. If the technician sees no water exiting the exhaust at idle, the FIRST component to inspect is:
Answer: The raw-water impeller
No exhaust water at idle almost always points to a failed raw-water impeller, as this pump is the first component that must move water before it can reach the exhaust outlet.
Which type of fuel tank vent system is required by ABYC standards to prevent siphoning of fuel overboard?
Answer: A looped vent line with its highest point above the fuel tank fill neck level
ABYC E-11 requires the fuel vent line to loop above the fuel tank fill level so fuel cannot siphon out through the vent if the vessel heels or the vent is submerged.
A technician measures intake manifold vacuum at idle and finds it cycling between 15 and 0 in. Hg. What fuel system fault could cause this reading?
Answer: A collapsing fuel supply line creating intermittent fuel starvation
A collapsing fuel line collapses under pump suction, momentarily cutting fuel flow and causing the engine to stumble; the line re-opens and flow resumes, producing a cycling vacuum gauge.
In a marine closed-cooling system, what is the purpose of the recovery/overflow bottle?
Answer: To capture coolant expelled when hot and return it to the system as it cools, maintaining correct coolant level
As the engine heats up and coolant expands past the cap's pressure rating, it overflows into the recovery bottle; when the engine cools, it is drawn back in, preventing air ingestion.
What condition can cause a marine engine's cooling water tell-tale (indicator stream) to produce a weak, intermittent stream even when the impeller is new?
Answer: A partially blocked tell-tale orifice or hose kink in the indicator line
The tell-tale orifice is small and easily clogged by marine debris or scale, producing a weak or intermittent stream even when the impeller pumps full flow.