Fuel, water and power capacity are calculated from a modelled itinerary, never from a rule of thumb. Take the real route, add a weather diversion allowance, apply the engine curve at your intended cruise, add generator consumption for the hours the plant will actually run, then hold a reserve. On Raja Ampat expedition itineraries the reserve is deliberately generous, because there is no refuelling option between Sorong and Wayag.
Step 1 — Model the itinerary in nautical miles
Write down each leg of the trip you intend to sell, in miles, then add three things owners routinely forget: repositioning between dive sites during the day, the return leg, and weather diversions. On a 12-day Misool and Wayag loop those additions can easily add 20% to the headline distance.
Then decide the cruise speed you will actually use — the economical band identified during design, not the maximum. See engine and propulsion choices.
Step 2 — Convert miles into fuel
Consumption comes from the engine manufacturer’s curve at the load corresponding to your cruise speed. Multiply through the modelled distance, then add:
- Generator fuel. On a liveaboard this is often 30–45% of total consumption, because generators run at anchor while mains do not.
- Manoeuvring and repositioning. Short high-load bursts at anchorages, dive site approaches and tender operations.
- A reserve. For expedition itineraries with no resupply, a reserve of 20–25% of calculated need is a defensible starting point, and more where weather routinely forces route changes.
Worked example: 30 m dive liveaboard, 12-day loop
| Component | Basis | Indicative volume |
|---|---|---|
| Main engine transit | ~520 nm modelled at economical cruise | Largest single block |
| Repositioning and manoeuvring | ~15% added to transit | Moderate |
| Generator hours | 12 days, hotel load at anchor and underway | 30–45% of total |
| Reserve | 20–25% of calculated need | Non-negotiable |
The proportions matter more than absolute litres, which depend entirely on hull, machinery and specification. The key insight is that generators frequently consume as much as the main engines on an expedition liveaboard — so anything that reduces generator hours reduces required fuel volume, which reduces tank size, weight and cost. That is the real argument for solar (solar and battery options) and for serious insulation (air conditioning design).
Step 3 — Freshwater
Guest water consumption on a dive vessel is consistently underestimated. Count showers after every dive, camera and gear rinse, galley and laundry, and crew usage. A realistic per-person-per-day figure on a dive liveaboard is far above hotel norms.
Two strategies exist and most vessels use both:
- Tankage. Simple, reliable, no maintenance dependency — but heavy and volume-hungry, and it competes directly with fuel for hull space.
- Watermaker. Converts electrical power into water, so it trades tank volume for generator hours. Specify realistic output, proper pre-filtration, and a plan for maintenance and membrane spares.
The sensible arrangement is a watermaker sized for daily demand plus tankage covering several days of failure, so a membrane problem is an inconvenience rather than a cancelled trip. Run the watermaker when generators are already loaded for other reasons.
Step 4 — Generator sizing from a load table
Build a load table listing every consumer, its power draw, and the hours per day it runs: air conditioning, compressors, watermaker, refrigeration, galley, lighting, navigation, pumps and charging. Then look at coincident load — what actually runs together — rather than the sum of everything.
Rules that hold on almost every Raja Ampat liveaboard:
- Two generators minimum. A single generator failure on a 12-day trip with air conditioning is a cancelled charter.
- Size for the real coincident load, not the theoretical maximum, so the set is not chronically underloaded — which causes wet stacking and shortens life.
- Sequence heavy loads. Compressors, watermaker and laundry can be scheduled so peaks do not coincide, allowing smaller sets.
- Plan night-time load separately. Guests sleeping with air conditioning is the load that determines whether a generator runs all night — and whether they sleep at all.
Step 5 — Check the weight and trim consequences
Fuel and water are heavy, and their consumption changes trim and stability across a trip. Tank arrangement must keep the vessel in acceptable trim both full and near-empty, and the stability calculation must consider free surface effect in partially filled tanks. This is a naval architecture task, not a plumbing decision, and it is one of the reasons tankage cannot sensibly be added after the hull form is settled.
Framework: technical specifications. Vessel context: liveaboard new-builds. To model your itinerary, contact +62 811 3823 875 or sales@komodoluxury.com.
Frequently Asked Questions
How much fuel capacity is needed for month-long Raja Ampat expeditions without refuelling stops?
Capacity is calculated from the modelled itinerary: real leg distances plus repositioning and weather diversion allowance, engine consumption from the manufacturer curve at your economical cruise, generator fuel for the actual hours the plant runs, and a reserve of at least 20 to 25 percent. On liveaboards generators often account for 30 to 45 percent of total consumption.
Should a liveaboard carry water tanks or a watermaker?
Both. A watermaker sized for daily demand trades tank volume for generator hours, while tankage covering several days of failure means a membrane problem is an inconvenience rather than a cancelled trip. Run the watermaker when generators are already loaded for other reasons.
How many generators does a dive liveaboard need?
At least two. A single generator failure on a twelve-day trip with air conditioning ends the charter. Size the sets from a load table based on coincident load rather than the theoretical maximum, so the units are not chronically underloaded.
Why does tankage have to be decided before the hull form?
Because fuel and water are heavy and their consumption changes trim and stability across a trip. Tank arrangement must keep the vessel in acceptable trim both full and nearly empty, and free surface effect in partially filled tanks feeds into the stability calculation. It is a naval architecture decision, not a plumbing one.