Where candidates go wrong
Candidates quote a fuel figure from memory ("we burn about 200 litres an hour") and stop. The examiner wants a method: from the passage plan to a number, for every consumable, with a margin you can defend. On a small yacht you are the whole engineering department, so nobody else will check your sums.
Start from the passage plan
| Input | Where it comes from |
|---|---|
| Distance and route | Master's passage plan |
| Speed | Economical speed agreed with the master, not maximum |
| Time at sea | Distance divided by speed |
| Weather allowance | Head seas and fouling raise consumption |
| Port calls | Where you can top up, and whether the fuel there meets the grade |
Worked example: fuel
A 1,200 nm passage at 12 knots takes 100 hours.
| Consumer | Rate | Hours | Litres |
|---|---|---|---|
| Two main engines at passage load | 190 l/h combined | 100 | 19,000 |
| One generator | 25 l/h | 100 | 2,500 |
| Total | 21,500 | ||
| Reserve, 20% (company policy example) | 4,300 | ||
| Required | 25,800 |
At a density of 0.845 kg/l that is about 21.8 tonnes. Compare it with usable capacity, not the brochure figure: fuel below the suction bell or trapped in wing tanks in a seaway is not fuel you can burn. Check also that the transfer arrangement lets you draw from each tank in turn without upsetting trim.
TIP — Measure your own consumption Modern electronic engines report fuel rate. Log it against rpm and load on every passage and you will have your own curve, which is worth more than the maker's.
Grade and quality
Fuel for the Mediterranean must meet 0.10% m/m sulphur since the Med became a SOx ECA on 1 May 2025. Plan where you bunker, what grade, and how you will prove it (see Bunkering: the chief engineer's responsibilities).
Everything else
| Consumable | Plan against |
|---|---|
| Lubricating oil | Top-up consumption plus one full change for each engine and generator that will reach its change interval |
| Filters | Fuel, oil, air, water-separator elements, at least one full set per engine plus spares |
| Coolant and treatment | Enough to refill the largest circuit |
| Hydraulic oil | Steering, stabilisers, thrusters, cranes |
| Fresh water | Persons on board x daily use, against watermaker output |
| Watermaker | Pre-filters, membranes, chemicals |
| Sewage and cleaning chemicals | Days at sea |
| Refrigerant | Only if you hold the certification to handle it |
Water example: 18 people at 200 l a day need 3,600 l/day. Two watermakers at 125 l/h each give 250 l/h, so the plant must run 14.4 hours a day. Keep a tank reserve in case a watermaker fails mid-ocean.
Stores and expendables
Rags, absorbents, gaskets, O-rings, impellers, belts, fuses, lamps, batteries, sealants, anodes. On a transatlantic delivery with no ports, the stores list is a safety document.
Telling the master
Put the result in writing: quantities, reserve, assumptions (speed, weather, generator load) and the point of no return if consumption runs high. The REG Yacht Code expects simple procedures for passage preparation, including equipment testing before sailing (23A.12).
What the examiner wants to hear
A method from passage plan to quantity; usable not total capacity; a reserve you can justify; the right fuel grade for the ECA; every consumable covered against running hours; and the result given to the master with its assumptions.