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.

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.

so many variables and inaccuarcies in fuel sending units/gauges..
Tank has a v bottom so the bottom holds less than the top..
If you are lucky, you get the sending unit to show full just as it spits. Usually it pegs full several gallons before it spits.(or it never pegs full)

fuel tank positioning... even when it spits full you don't really know exactly what you have.
If you are at a fuel dock by yourself, you are listing toward the filler. if you have a buddy standing on the bow with a line you are bow down...

estimates of gph

well, none of us are going to spend a day making precise 10 mile runs at 1000 rpm increments with precise measured fuel, charting out gph and mph and mpg...
and if it gets snotty, it won't mean a thing...

What you need is a fancy new 4 stroke with a computer readout to tell you gph and help you calculate out range at a given speed.
I ran a YamahaF250 this summer and it had a guage that did that....sweet:love:

I wish I could add a Flow Scan but I don't believe they will work on a fuel injected motor with a 2 stage -low and high pressure- fuel pump system.

I need to upgrade to a 2017 DF150 zuki with all the bells & whistles :sly:

Yes to all that.........and plus........if you have a working fuel gauge and know how many gallons the tank holds, refill when the gauge shows 1/2 full.

This way you'll know approx. how accurate it is.......if you have a 60 gal tank and it refills taking 30 gallons, well then your gauge is accurate.

Do it again when it shows 1/4 tank and see if it's still reading accurately.....and takes approx. 45 gallons to refill.

Most all the flow sensors will work with the efi outboards with 2 pumps except for some yamaha's. Some yamaha's don't run the low pressure all the time, but instead pulse it. The total fuel used will be correct, but the gph at any given time will be off. Just about ANY engine can have a fuel flow meter on it. I had one on my old 85 140 evinrude. Loved having that floscan, really changed how I ran the boat as what I thought was optimal speed wasn't. Found it liked to go alot faster than I'd guessed to get the best economy.

My offshore trolling trips cover an average of 110-130 miles. With a 200 hp 2-stroke I burn a very consistent 1.8 miles to the gallon. Given winds, current, and seas, there are so many variables to try and calculate from charts. I find the conditions are my speedometer more than anything else. Fuel consumption is easily forgotten when that massive thunder head pops up out of nowhere.