Engine Fuel Consumption Calculator
Calculate fuel consumption and efficiency for marine engines.
How to calculate marine engine fuel consumption
Fuel burn rises with engine power and how hard you're working the engine. A reliable estimate uses a specific fuel consumption rate per horsepower, scaled by the load you're running:
Litres per hour = HP × rate × load factor
The calculator uses about 0.21 L/hr per HP for diesel and 0.29 L/hr per HP for petrol, then multiplies by your load percentage. Diesel engines are more efficient per horsepower, which is why they dominate larger vessels.
Worked example
A 150 HP petrol outboard cruising at 70% load: 150 × 0.29 × 0.70 ≈ 30 litres per hour. Over a 3-hour trip that's about 90 litres. The same engine at wide-open throttle (100% load) would push past 43 L/hr — so easing back to a cruise saves roughly a third of your fuel.
Typical fuel consumption by engine size
| Engine | Cruise (≈70%) | Full throttle |
|---|---|---|
| 60 HP petrol | ≈ 12 L/hr | ≈ 17 L/hr |
| 115 HP petrol | ≈ 23 L/hr | ≈ 33 L/hr |
| 250 HP petrol | ≈ 51 L/hr | ≈ 73 L/hr |
| 260 HP diesel | ≈ 38 L/hr | ≈ 55 L/hr |
How to cut fuel consumption
- Cruise at 70–85% load — the most efficient band for most engines.
- Keep the hull and prop clean; fouling can add 10–15% to fuel burn.
- Trim correctly and don't carry unnecessary weight.
- Service annually — fouled injectors and worn impellers waste fuel.
To turn litres per hour into a trip budget, use the fuel trip cost calculator, or see efficiency per nautical mile with the fuel economy calculator.
Note: actual consumption varies with engine condition, weather, loading and hull state.
Planning a trip? Get the offline Fuel & Range Planner
Fuel burn, range, tank capacity and trip cost. Offline in Excel or Google Sheets. From A$19.99 (approx. US$12).
See what's insideFrequently Asked Questions
How much fuel does a marine engine use per hour?
As a rule of thumb, petrol outboards use about 0.4 L/hr per HP at full throttle, and diesel engines about 0.25 L/hr per HP. At cruising speed (60-70% throttle), consumption drops by 30-40%.
Does engine age affect fuel consumption?
Yes. Poorly maintained engines can use 10-15% more fuel due to fouled injectors, worn impellers, and carbon buildup. Annual servicing helps maintain efficiency.
Is a 4-stroke engine more fuel efficient than a 2-stroke?
Modern 4-stroke outboards are typically 30-50% more fuel efficient than older 2-stroke carburettor models. Direct-injection 2-strokes like the Evinrude E-TEC are comparable to 4-strokes.