The boat fuel economy calculator estimates your boat's fuel consumption in gallons per hour (GPH), range, and fuel cost at different speeds. Plan your day on the water without running out of fuel or blowing your budget.
Calculate Boat Fuel Economy
Understanding Boat Fuel Economy
Boat fuel consumption is much less efficient than cars — most recreational powerboats get 1-6 miles per gallon at cruise speed. The key factors are engine size, hull type, speed, load, and sea conditions.
Speed vs. Fuel Economy
Most planing hulls have a "sweet spot" just above plane where fuel economy is best — typically 22-32 MPH. At idle (displacement speed), miles per gallon is actually very poor because you spend a long time to cover each mile. At WOT, consumption spikes dramatically. Find the rpm that corresponds to 70-75% throttle and record the fuel burn — this is your efficient cruise setting.
Fuel Planning
Never use your full tank capacity for range planning. Use 90% of tank capacity for maximum range, then apply a 25% safety margin for range planning. Always know where your next fuel stop is. On coastal or inland cruising, carry a hand-held VHF radio and file a float plan so someone knows your route and expected return time.
Frequently Asked Questions
Is this boat fuel economy calculator free?
Yes, completely free with no signup required.
How is boat fuel consumption calculated?
A common rule of thumb: a gasoline engine consumes about 0.5 gallons per horsepower per hour at wide-open throttle (WOT). At cruise (75-80% throttle), consumption drops to 0.4 GPH/HP. So a 150 HP engine burns about 60 GPH at WOT and 45 GPH at cruise. Actual consumption varies by hull type, load, and sea conditions.
What speed gives the best fuel economy?
Most outboard-powered boats achieve best fuel economy just above plane speed — typically 22-32 MPH for recreational boats. This is where the hull rides on top of the water rather than pushing through it. At idle (in-the-hole) speed, fuel consumption per mile is often the worst. At very high speed, drag increases dramatically.
How do I calculate my boat range?
Range (miles) = (Fuel capacity × 0.9 ÷ GPH) × Speed. Use 90% of capacity to leave a safety reserve. Example: 50-gallon tank, 6 GPH, 25 MPH = (50 × 0.9 / 6) × 25 = 187.5 miles. Always plan for winds, current, and unexpected detours by only using 75% of calculated range.
Does ethanol in marine fuel reduce performance?
E10 fuel (10% ethanol) is the standard at most gas stations and reduces fuel economy by 3-5% vs. pure gasoline because ethanol has less energy density. E15 is not recommended for marine engines in most cases. Use ethanol-free fuel (recreational marine fuel) when available for best engine performance and to reduce moisture absorption in the tank.