Question 1

List the correct pre-departure engine checks in the order they should be performed

Accepted Answer

1. Engine oil level (dipstick, between min and max); 2. Coolant level (header tank, cold engine); 3. Raw water seacock open; 4. Raw water strainer clear; 5. V-belt condition and tension; 6. Fuel level; 7. Battery voltage; 8. Bilge — no excessive water; 9. Start engine, check exhaust water flowing within 30 seconds, watch temperature gauge and oil pressure; 10. No unusual noises or smells before departing The pre-departure engine check takes 3-4 minutes and should be as automatic as checking tide times. The most commonly missed items: raw water seacock (closed accidentally in the marina for some reason), raw water strainer (choked with weed overnight on the pontoon), bilge water level (high bilge can indicate a problem), exhaust water check after start. The exhaust water check is the one most sailors forget — it confirms the entire raw water circuit is functioning before the vessel leaves the berth, not 10 miles offshore.

Question 2

What is the fundamental operating principle of a diesel engine that distinguishes it from a petrol engine?

Accepted Answer

Compression ignition: diesel fuel is ignited by the heat of highly compressed air (compression ratio ~22:1) — no spark plugs are used. Fuel is injected into the compressed air at the moment of ignition Diesel (compression ignition): air is compressed to ~22:1 ratio, reaching ~500-700°C. Diesel fuel (which ignites at ~250°C) is injected directly into this hot compressed air and spontaneously ignites. Petrol engines use ~8:1 compression and require a spark to ignite. The high compression ratio makes diesel engines more thermally efficient (~40% vs ~25% for petrol) and safer (diesel is much less volatile than petrol).

Question 3

Describe the four strokes of a diesel engine cycle in the correct order

Accepted Answer

Induction (air in): piston down, air drawn into cylinder. Compression: piston up, air compressed to high temperature. Power (ignition): fuel injected, combustion drives piston down. Exhaust: piston up, exhaust gases expelled The four-stroke diesel cycle (suck, squeeze, bang, blow): 1) Induction — intake valve open, piston moves down drawing in air only (no fuel). 2) Compression — both valves closed, piston moves up, air compressed to ~22:1. 3) Power — injector fires, combustion, piston driven down. 4) Exhaust — exhaust valve open, piston moves up expelling gases. Two complete crankshaft revolutions per power stroke per cylinder. Multiple cylinders provide smoother, overlapping power strokes.