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Starting, Running & Shutting Down
💡 Start with a fixed checklist, confirm cooling water and oil pressure within seconds, watch temperature and charge underway, and shut down by idling then cutting the fuel.
A marine diesel has no spark plugs — recall from earlier that it fires by compression, so starting is about giving it fuel, air, cooling water, and a strong crank. Work a fixed pre-start checklist every time: put the gearbox in neutral, turn on the battery isolator and fuel valve, open the raw-water seacock (the through-hull that feeds cooling water), and glance at the dipstick and coolant level. Then turn the key — many small diesels need you to hold a heater/preheat position for a few seconds first — and crank.
The instant it fires, run three checks. Look astern: cooling water should be spitting from the exhaust within 10–15 seconds. Watch the oil-pressure gauge or light — pressure must come up almost immediately; if the warning light stays on, stop at once. Let it idle to warm up before you load it.
Underway, scan the gauges every few minutes. Coolant temperature should settle in the normal band (often around 75–85 °C) and stay there; a steady climb means a cooling problem. Oil pressure should hold steady, and the voltmeter/ammeter should show the alternator charging (around 13–14 V). To shut down, drop to idle for a minute or two so the turbo and hot metal cool evenly, put the gearbox in neutral, then pull the fuel stop (a diesel is killed by cutting fuel, not by turning off a spark). Finally close the seacock if you're leaving the boat.