Also, remember that engines with direct and electronic fuel injection will yield higher fuel efficiency. Fuel consumption will be decreased at cruising speeds. Keep in mind that these formulas apply when the engine is making peak rated horsepower, which usually is at wide-open throttle (WOT). GPH = (specific fuel consumption x HP)/Fuel Specific Weight They are a rough estimate of what your fuel consumption will be.įormula To Estimate Maximum Engine Fuel Consumption Let’s look at the mathematical calculation below for an explanation. But they provide an excellent relative difference between engines when shopping. These figures don’t take drag of the boat, sea conditions, or efficiency losses through transmissions and bearings into account. Likewise, a well-maintained diesel engine burns about 0.40 pounds of fuel per hour per horsepower. On average, a four-stroke gasoline engine will burn about 0.50 pounds of fuel per hour per horsepower. This makes it important to know that ethanol free gasoline weighs about 6.2 pounds per gallon and diesel fuel about 6.9 pounds per gallon. Fuel efficiency is measured in gallons of fuel used per horsepower by per hour. This gives the ability to estimate fuel usage based on the throttle position.

Many of today’s marine engines have fuel flow readouts. Weather and sea conditions vary more than road conditions, the time it takes to cover a distance varies more, so fuel consumption is measured in gallons per hour rather than miles per gallon.

Calculating fuel consumption on a boat is much different than your own car.

Free gas mileage calculator