Boat Fuel Calculator
Fuel (GPH)
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Trip Fuel
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Trip Time
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NM per Gallon
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Estimating Boat Fuel Consumption
Gas engines: ~0.10 GPH per HP. Diesel: ~0.055 GPH per HP. Actual varies with hull, sea state.
At 75% throttle, use 75% of max fuel rate. Most cruising is 65-80% throttle for best efficiency.
Rule of thirds: 1/3 out, 1/3 back, 1/3 reserve. Never use your reserve unless emergency.
Frequently Asked Questions
How to calculate boat fuel?
HP x SFC (0.10 gas, 0.055 diesel) x throttle%. 150 HP gas at 75%: 11.25 GPH.
Rule of thirds?
1/3 fuel out, 1/3 back, 1/3 reserve. Plan trips within 2/3 of tank capacity.
Why diesels use less?
Higher thermal efficiency (35-45% vs 25-30%) and diesel has 10% more energy per gallon.
Speed vs fuel?
Fuel increases roughly with cube of speed for displacement hulls. Doubling speed uses ~8x fuel.