Fuel rate ?

[wilbur1]

I installed a interface cable to connect my 2015 115 to Lowrance HDS 10. At WOT throttle trimmed its reading 10 gal. per hr. Does this sound right.?

[2014DF25ARS]

It’s certainly in the ballpark. I’ve heard a rule of thumb that an outboard motor at WOT will burn about a gallon of fuel per hour for every 10 HP. So 10 gal/hr for 115 HP seems a reasonable fit. My DF25A burns about 2.5 gal/hr at WOT. With the gauge, I’ve learned that my MPG improves by about 40-50% when I back off to 2/3 throttle.

[Moonlighter]

Hi Wilbur

I rarely look at fuel flow any more on my DF115 (2010 year) because I think that fuel economy is a more useful measure.

If you set your HDS up to show mpg you will soon see the most economical speed to travel. On my boat its around 4200rpm, but if doesnt actually drop much up to 5000rpm, greater than that rpm though, it dips off quite steeply.

The only time I have looked at fuel flow is initially when setting up the network, and fuel flow in a 115 at idle, should be around 0.8 litres per hour. Or imperial equivalent.

Anyway your figures sound roughly OK.

Because all the fuel data is all drawn from one data source, fuel flow and fuel used are all directly related, so if flow is accurate, fuel used is accurate, and vice versa. Accuracy doesnt change with rpm, it is a constant.

If you want to check your fuel data accuracy and fine tune it by calibrating, there is only 1 way to do it, as follows:

1. Fill your fuel tank and set to full in the fuel menu.

2. Go and burn at least 1/4 tank, but the more, the better. You need to burn at least 5 gallons absolute min.

3, Go back to the same gas station immediately after finishing the trip and preferably same pump, fill again, try to fill to same “fullness” as last time.

4. Then, in the fuel menu, compare the amount the system says was used with what you actually put in. If there is a vaiation between the 2 figures, calibrating will improve accuracy. Select set to full, enter, then select calibrate. Select the engine to calibrate, then it will pop up a menu where you enter in the actual amount added at the pump. Complete the process. (You can probably understand now why its best to use as much fuel when calibrating as possible)

You may have to do this process 3-4 times to get it close to perfect accuracy, but dont do it more than 5 times.

If you get it within 1-2% accuracy then I would leave it alone, because the variation then is more likely due to how full you fill the tank, and that is often related to the ground level at the gas station, loss thru evaporation etc.

By the way, evaporative loss can be an issue, so if you are calibrating the system its very important to fill up immediately after a trip and do the calibration then, and not to leave the refuel for weeks afterwards, as evaporative loss from a part filled tank can be quite significant and will affect your data.

[tsturm]

My DF-175 burns 17gph @ WOT

[wilbur1]

Thanks Guys I appreciate it. It just seemed like a lot to me. I cant even imagine what a 2 stroke would be,. Thanks Again

[Moonlighter]

What rpm are you getting at WOT trimmed out?

[wilbur1]

5900-6000 rpm

[Hoosmatroos]

That sounds about right. Boats use a lot of gas, especially at WOT