Engine checks
How to Check a Boat Engine Before Sailing — The Daily Checks
Published · Last checked October 2026
Before starting a yacht's diesel engine, run through the daily checks often remembered as FOWLBELT: Fuel level and filter, Oil level on the dipstick, Water (raw-water seacock open, coolant level), Leaks and bilge, Belts tension, Electrics (battery switch on), Lines in the water around the prop, and Transmission in neutral. After starting, check that cooling water is coming out of the exhaust. These five-minute checks prevent most engine failures at sea.
Why check the engine every day
Most RNLI call-outs to sailing yachts involve machinery failure, often from simple causes: no fuel, dirty fuel, a closed seacock or a slipping belt. A daily check takes a few minutes and is the core of the engine checks lesson.
The FOWLBELT checks
| Letter | Check | What you are looking for |
|---|---|---|
| F | Fuel | Enough for the passage plus reserve; water trap in the filter clear |
| O | Oil | Engine oil between the dipstick marks; gearbox oil if a dipstick is fitted |
| W | Water | Raw-water seacock open, strainer clear, coolant header tank topped up |
| L | Leaks | No oil, fuel or water in the engine tray or bilge |
| B | Belts | Alternator and water pump belt tight, about 1 cm of deflection, not glazed |
| E | Electrics | Battery isolator on, connections tight |
| L | Lines | No ropes in the water near the propeller |
| T | Transmission | Gear lever in neutral before starting |
Starting and after starting
- Throttle slightly open, gear in neutral.
- Preheat with the glow plugs if fitted, typically 10 to 20 seconds.
- Start, and release the key as soon as the engine fires.
- Check the oil pressure warning light and charge light go out.
- Look over the stern: a steady flow of cooling water must come from the exhaust. If not, stop the engine and investigate.
- Let it warm up at low revs before putting load on it.
Under way
- Listen for changes in note and watch the temperature gauge and alarms.
- Check the exhaust water flow from time to time.
- On long motoring passages, check the bilge and engine space every few hours.
- Carry spares: impeller, belts, fuel filters, and the tools to fit them.
A deeper look at how a diesel works, bleeding fuel systems and changing impellers is in the Coastal Skipper diesel engine lesson.