Elling range and fuel consumption: reading the numbers

Why range is a curve

Fuel consumption is often quoted in gallons per hour, but passage planning is clearer in fuel per nautical mile. A boat burning fewer gallons per hour may still be less efficient per mile if it is moving much more slowly. Conversely, adding only a few knots in the semi-displacement band can demand a large increase in power and fuel per mile.

For a first approximation, theoretical still-water range equals usable fuel divided by consumption per nautical mile. The important word is usable. Tank capacity on a specification sheet is not necessarily the amount that can be safely drawn in waves, and prudent passage planning leaves a reserve rather than treating the final gallon as available propulsion.

What the published Elling figures tell us

For the E3 and E4, a historical factory reference point illustrates economical displacement-speed operation. At approximately 7.5 knots, 1 liter per nautical mile paired with a 1,500-liter tank produces the familiar 1,500-nautical-mile theoretical figure. At higher semi-displacement speeds, fuel consumption rises sharply and range falls accordingly.

The E6 is a substantially larger yacht with 5,000 liters of fuel. Current published factory guidance indicates approximately 2,500 nautical miles at 9 knots. That is a useful comparison point, not a guarantee. Before delivery, we provide the current factory data for the selected propulsion package and encourage owners to build their own log from actual fills and miles traveled.

What must be deducted before departure

Start with a reserve appropriate to the route, weather uncertainty and availability of alternates. Then account for fuel that may be unusable because of tank geometry and vessel motion. Add generator or diesel-heating consumption if those systems draw from the same supply. Consider adverse current, head seas, wind, stabilizer load, a tender or cruising gear, bottom growth and a propeller that is not perfectly clean.

A long offshore leg also needs a diversion allowance. If the destination entrance becomes unsafe or a fuel dock is unavailable, the yacht must be able to reach the next acceptable option. The reserve is not wasted capacity; it is the margin that keeps a changing situation from becoming an emergency.

• Navigation reserve and diversion distance
• Generator, heating and other diesel consumers
• Adverse wind, current and sea state
• Cruising load, tank accuracy and unusable fuel
• Hull and propeller condition

Build a trustworthy onboard performance table

Begin with clean running gear, known tank levels and a representative cruising load. On reciprocal headings in settled water, record speed through water, speed over ground, rpm and stabilized fuel flow at several operating points. Reciprocal runs help reduce the effect of wind and current. Repeat the exercise after the yacht is fully provisioned and compare the results.

The outcome should be a simple table kept at the helm: expected fuel per mile, conservative range after reserve and estimated hours for each normal speed. That table is more valuable than a single maximum-range claim because it turns the Elling’s broad speed envelope into an informed operational choice.