Consumed with fuel consumption

[studlymandingo]

After installing the Navman fuel flow transducer on my boat, I finally took it out for a run this afternoon. I switched the GPS unit (Navman 5500 TFT) over to the fuel monitoring screen and ran at various speeds and trim settings to see what my fuel usage was under varying conditions. It didn't take long for obsession to take control and I spent the next couple of hours trying to get the best fuel economy. Depending on the wind and a few other factors I determined that the best fuel economy was in the 32-33 MPH range. My 150 Mariner would get about 4.8 MPG there.

All in all, it was pretty scary seeing just how much fuel was going into that motor; so I switched her back to the chartplotter mode, bumped up the throttle, and enjoyed the wind in my face!

 

[Boomyal]

Re: Consumed with fuel consumption

What is it they say? The ignorance of fuel consumption is the beginning of happiness.

I'd really like to see what a 300 cu in V8 would get under the same circumstances.

 

[QC]

Re: Consumed with fuel consumption

Cool. Great fuel economy. Is that a comfortable cruise speed? You should try it with your tabs up. That would be interesting . . . I think you have them, right?

 

[studlymandingo]

Re: Consumed with fuel consumption

What is it they say? The ignorance of fuel consumption is the beginning of happiness.

Exactly!!!

QC, I do have tabs, I think I'll try it without them engaged and see what happens. I'll post the result.

 

[jtexas]

Re: Consumed with fuel consumption

6.7 gallons per hour...what % of WOT RPMs was that?
How much do you save over WOT at that speed?
If you didn't plot a curve, then you weren't really consumed by it.

 

[Silvertip]

Re: Consumed with fuel consumption

JT -- I will wager It was nowhere near WOT. Using a Navman 2100 fuel flow monitor, my 75 Merc will burn exactly 7.5 gph @ 42 MPH at WOT, two people, full fishing gear, and a full live well. Funny how that rule of thumb of putting a decimal point one position left in the HP rating will provide GPH @ WOT. Cruising at 30 - 32 MPH will suck up 5.2 GPH.

 

[studlymandingo]

Re: Consumed with fuel consumption

I'll try to post some more readings soon. I was going to chart all the info today, but I had an outboard issue that prevented me from getting over 7 MPH; not at all conducive to this type of testing.