Originally Posted by 7075T6

My 44 ft raceboat, with 2 x FPT 560, gets 1,43 mpg at 80 mph and 1,26 at WOT(85-88 mph depending on fuelload).
Never more than 1,65 mpg at any speed. Boat weighs 11000 lbs raceready, 220 gal of fuel, no crew.

http://www.offshoreonly.com/forums/g...ce-diesel.html

Originally Posted by pstorti

I think your constants may be good for theory but off for the real world. my engines (315 hp each, 1.7-1.8 @ 53mph) are supposed to burn 16gph at wot but usually it is closer to 15. The Hustler has a more efficient hull than a regular boat the diesels may normally be installed in and they may not be 100% loaded at top speed. I don't know what they are using to measure the fuel rate maybe there is some error there as well. I have Maretron sensors that measure the supply and return rates along with temperature of the fuel to compensate for volume changes to get very exact numbers, unfortunately the stupid Garmin's only give me to tenths not hundredths, but if it is showing 1.7 to 1.8 I know the real number is closer to 1.75, as it rounds up and down.

Originally Posted by Michael1

In your case, your measured fuel rate is 1 - (15/16) = 6.6% lower.

In the case I presented, the claimed fuel economy is 2/1.35 = 48% higher!

The constants aren't off any where near that amount. For instance, diesel fuel may range from 6.9 to 7.1 pounds per gallon, and the BSFC range doesn't account for it either.

Michael

Originally Posted by pstorti

Even at lower speeds you don't get better economy? what about at 40 or 50 mph?

Originally Posted by pstorti

That's a good point, hopefully somebody from Hustler will chime in, we all know boat manufacturers tell it like it is with no exaggeration