1974 Evinrude Fuel consumption

[robthompson66]

Hi there

I have a 1974 evinrude 115 horse on a late 60's 16 foot thompson v hull runabout that weighs around 1400lbs loaded. My fuel consumption seems a bit excessive and just wondered if anyone knew if this was normal or not. I use about 7.5 gallons per hour at 24mph, and around 10-11g/hr at wide open which is about 32mph. I was out last Sunday morning for about 2-1/2 hours, averaged 15 mph and used 12 gallons of fuel. I have a 13-1/4 x 19 prop right now. I don't know my rpms because my tach doesn't work, I have a new rectifier, but still no tach.

Thanks!

 

[tashasdaddy]

Re: 1974 Evinrude Fuel consumption

". I use about 7.5 gallons per hour at 24mph, and around 10-11g/hr at wide open" this is normal. at 15 you are probably lugging the motor. the prop is the average prop for that motor.

 

[robthompson66]

Re: 1974 Evinrude Fuel consumption

Thanks for the quick response!

Rob

 

[HighTrim]

Re: 1974 Evinrude Fuel consumption

Rob the rule of thumb for finding fuel consumption for an outboard is to take the total HP and divide it by 10. That will give you an approximate GPH (gallons per hour) at WOT (wide open throttle). In your case, that is 11.5 GPH at WOT.

The more complicated way starts by knowing the fuel weighs about 6 pounds per gallon. A well-maintained two-stroke outboard burns nearly 0.6 to 0.8 pounds of fuel per hour for each unit of horsepower it produces. In your case, this would mean that for your particular outboard, it would burn about 11.5-15.3 GPH at WOT.

Either way you do it, you are about right. And remember, these figures are for WOT speeds, and are an average, they may vary within 10 percent or so. These figures will drop when cruising as well. They are also mainly for the crossflow systems, as the newer loop charged or fuel injection systems are a bit more fuel economical.