MPG chart.

[THEFERMANATOR]

Originally Posted by tsubaki

The actuality of it is, how it always was.
The faster you can go while consuming the least amount of fuel, the farther you can go.

The gph gauge was very important to me since I have only 2/20 gallon saddle tanks.
If I was fishing offshore and I was pressed for time to get back without running out of fuel I could calculate my available range by the gph/mph chart.

Our dock is 15 miles from the sound and around here we need to run another 6 miles to the first offshore reef which is in only 30' of water.
The next nearest reef is 10 miles offshore but it's in only 40' of water.
To get into some decent fish we need to be about 25 miles offshore and at that it's only 55' deep.

So you figure if I was wanting to fish 25 miles offshore and if I was able to maintain 30mph at 11.06gph (2.71mpg) I could go 108 miles on 40 gallons of fuel. The actual trip would be 80 miles and consume 30 gallons of fuel.

See why I was so worried about the fuel consumption?

Just wished we had water that deep at those distances. 20 miles gets you 25 feet of depth, 40 miles gets you mid 50-55 feet deep. Gotta head out around 65+ to get around 100 feet.

[SkunkBoat]

Originally Posted by THEFERMANATOR

Just wished we had water that deep at those distances. 20 miles gets you 25 feet of depth, 40 miles gets you mid 50-55 feet deep. Gotta head out around 65+ to get around 100 feet.

take a road trip to Pompano Beach. 15 miles>1000ft ... Boat a sword on a V20

[jvitiel]

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

[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... :-)

[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.

[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.

[Destroyer]

Originally Posted by macojoe

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

Yep. My first V20 had that also. And that's exactly what I did. Same thing on my Cruisers, Inc. 19 footer. one 6 gal portable for emergencys, and the two saddle tanks.. one for going out, and the other for returning.

[jvitiel]

My gas gauge broke (it swung so wildly that the needle finally broke off!). Since then I have been happy just looking at the reading from the fuel flow meter and then just adding back in what it says I used. I mentioned this to someone and they said that's fine as long as no one steals your gas. Obviously a flow meter won't pick that up like a level gauge would so you might get stuck out there. My boat is stored next to my house so that's unlikely but it did give me pause.

On a related note. Is it common to have the gauges swing with the sloshing in the tank or was mine somehow missing a damping device, circuit or function? I have seen some that are smooth and some that bounce around like mine did. If I can be assured that a new one would be smooth I would probably replace it.