MPG chart.

[tsubaki]

Originally Posted by SkunkBoat

so MPH divided by GPH= the values in Miles per Gallon

IF you are travelling 1 mph @ 1gph you will travel 1 mile using 1 gallon in one hour

The chart doesn't do anything for you if you don't already know you gph rate at any given mph.

If you know your gph at a given speed you can use the chart to calculate range at a given speed.(if you accurately know how much gas you have)

If you accurately know your gph, you probably have a electronics telling you your range.

Exactly!
I was lucky enough to be within a gallon of my actual fuel level as to what the gauge said.
Having the gph fuel consumption device and something like a gps for mph was the only way to get close. Doing the math does the rest.

[tsubaki]

Originally Posted by BillTex

Oh yes...i do understand. For those of us that fish offshore range (- gph) is critical!

I was wondering if you have had the chance to prove your extrapolations.

And what was your baseline?

Thanks, Bill

There was no baseline, SkunkBoat pretty much covered it in post #8.
The chart is for at a glance as to your current mileage based on knowing your fuel consumption and speed.
Go back to my post #5, click on the link and see the pictures of my dash.
The device in the bottom center of pictures 5-7 is a Lowrance fuel flow device, the top right is a depth finder/gps. By knowing your speed and fuel consumption, math can do the rest.

[BillTex]

Originally Posted by tsubaki

There was no baseline, SkunkBoat pretty much covered it in post #8.
The chart is for at a glance as to your current mileage based on knowing your fuel consumption and speed.
Go back to my post #5, click on the link and see the pictures of my dash.
The device in the bottom center of pictures 5-7 is a Lowrance fuel flow device, the top right is a depth finder/gps. By knowing your speed and fuel consumption, math can do the rest.

OK...missed the part about the flow meter...that's what i was looking for!
Thanks, this is good info.

So the flowscan shows ~3900 rpm is the most efficient cruise speed.
When u get over 4k efficiency drops off.
Speed/rpm/efficiency is not linear!
Makes the math a little tricky.

Tx, Bill

[phatdaddy]

I have never had any flow meter info until i got this new motor. It's included in the smart guage. It really lets u fine tune speed vs fuel consumption. Pretty accurate too. When i fill up i am usually within 2-3 gallons on a 45 gallon fill up. I wish i had trim tabs to even tweak it a little more.

[jvitiel]

So I was thinking - If high salinity increases buoyancy, does that improve fuel economy?...

[bgreene]

My Evinrude Master Tech advised me not to install a fuel flow gauge.....said it restricted flow.
So, in order to confirm mpg, got to do it the old way.....fill......run......re fill divide into miles.

[Destroyer]

Originally Posted by jvitiel

So I was thinking - If high salinity increases buoyancy, does that improve fuel economy?...

I have no idea,
BUT...
Anything that will reduce the amount of friction between the hull and the water as the hull passes thru it will increase either the fuel economy or the speed (in the case of a sailboat) That's why sailboats (Especially racing ones) use special coatings on their hulls to reduce friction.

So that being said... if we postulate that higher salinity increases buoyancy then it should stand to reason that there would be a lessening amount of friction on the hull, which should result in better fuel economy. But since a hull's density is a lot different than human tissue (that is primarily water anyways) I question how much the effect of higher salinity on fuel economy would actually be.

[jvitiel]

Agreed. There is probably no practical difference or even anything that the typical boater could measure (though I bet NASA could measure it).

I'm guessing that the difference in efficiency would be most apparent in a displacement hull or at least when a planing hull is not on plane. The boat would sit higher in the water and therefore have less to push out of its way. Somewhat similar to decreasing the rolling resistance of a tire by inflating it more.

Still, a mitigating factor could be that the smaller volume of water that has to be pushed out of the way would also require more energy to move due to its added density. Who knows.

Truly a topic that I wouldn't give a second thought to if my boat wasn't stuck under a tarp... :-)

[THEFERMANATOR]

Originally Posted by bgreene

My Evinrude Master Tech advised me not to install a fuel flow gauge.....said it restricted flow.
So, in order to confirm mpg, got to do it the old way.....fill......run......re fill divide into miles.

The added restriction from a quality flow sender is negligeable at the most. But if you have an etec, theres no reason you can't get a a nmea 2000 gateway connection, and read the calculated flow rate from the emm.

[macojoe]

I have never had a working gas gauge!! Just filled up after every trip and never had a isue. When I had the 2 20 gal tanks I ewould run till the first was emoty then head back toward home.