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How much fuel do you really have in the tank??

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Old 07-21-2012, 10:51 PM
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Default How much fuel do you really have in the tank??

Wondering how accurate everyone's fuel gauges are?

My scarab has a single 130 gallon tank. The pickups and the sender are located at the rear of the tank. Between the sender being at the rear plus the angle in which my scarab sits in the water my fuel gauge reads full when there is about 60 gallons in the tank. And then the gauge falls aggressively as I burn fuel again because of the angle. Is this something everyone gets used to or is there more then one sender in other tanks and you average the readings?

Maybe this is normal?

Thanks
Jim
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Old 07-21-2012, 11:39 PM
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Every boat I have ever owned has been different. If I didn't install the gas tank I always have to take them out on empty with a 5 gal can of gas and see just how empty they will go.
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Old 07-22-2012, 07:14 AM
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What you also have to take into consideration is that most tanks have angled bottoms mirroring the inside of the hull bottom. That means that most tanks (mine is one)only carry approx. 30 - 40% of the fuel in the bottom 1/2 of the tank and 60% - 70% in the top half which has straight/square walls.
I ran my old Sonic out of gas several times until realizing this. Always seemed to do good on the 1st 1/2 tank and the gauge was validating this. Once you dropped bellow the 1/2 mark on the gauge the needle dropped twice as fast from there down.
That angle in the bottom of the tank was causing this.
I also just finished experimenting with sending units. Replaced the OEM version w/a Livorsi floatless version. Measure difference of ohm readings of an empty tube submerged in tank. It quit working (was a $100. TOO!) @ 30 hrs (more Livorsi garbage!) and just got replaced by the version w/a round float n a similar tube. No mechanical linkage to adjust and has far lees needle bounce.

Sorry for the book but been there, done that.
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Old 07-22-2012, 07:17 AM
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Originally Posted by Twin O/B Sonic
What you also have to take into consideration is that most tanks have angled bottoms mirroring the inside of the hull bottom. That means that most tanks (mine is one)only carry approx. 30 - 40% of the fuel in the bottom 1/2 of the tank and 60% - 70% in the top half which has straight/square walls.
I ran my old Sonic out of gas several times until realizing this. Always seemed to do good on the 1st 1/2 tank and the gauge was validating this. Once you dropped bellow the 1/2 mark on the gauge the needle dropped twice as fast from there down.
That angle in the bottom of the tank was causing this.
I also just finished experimenting with sending units. Replaced the OEM version w/a Livorsi floatless version. Measure difference of ohm readings of an empty tube submerged in tank. It quit working (was a $100. TOO!) @ 30 hrs (more Livorsi garbage!) and just got replaced by the version w/a round float n a similar tube. No mechanical linkage to adjust and has far lees needle bounce.

Sorry for the book but been there, done that.
+1
I have twin 130 gallon tanks. When the gauge reads 1/2 tank, I have about 50 gallons left.
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Old 07-22-2012, 07:55 AM
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Mine is the opposite of most...it shows empty with half a tank left
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Old 07-22-2012, 08:05 AM
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Originally Posted by tnc110
Mine is the opposite of most...it shows empty with half a tank left
Would almost rather have that problem, better safe then sorry!
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Old 07-22-2012, 08:14 AM
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I own these senders in both of my boats and they work excellent but they don't fix the issue I talked about initially. It doesn't have so much to do with the sender as it does simply with the shape and attitude of boat fuel tanks.

http://www.centroidproducts.com/

Well I feel a little better that it's not only me!

I suppose a second sender mounted mid tank would help to show fuel consumption above the 60 gallon mark. In theory if calibrated correctly the first sender would report 1/4 tank when the second sender would start to show movement off of the full mark
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Old 07-22-2012, 08:23 AM
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On my Formula 1/4 tank is empty. Don't ask me how i know. Jeff Wurl
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Old 07-22-2012, 08:38 AM
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My fountain stays on full along time and then drops to a half . When it hits a quarter look for gas it only last about 10 miles. I know for sure ran out a mile from the dock and I was down river from the dock it sucks.
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Old 07-22-2012, 01:00 PM
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On my 29' Fountain with 140 gallon tank it takes 10 gallons to go from 1/4 to 3/8s. If it were a linear add or drop it should take 17.5 gallons. I have gas cans filled in the garage. Next I will see what it takes to go from 3/8s to 1/2. I hope to get this all figured out this summer. Like "The Mayor" I don't think the last 1/4 tank will take the boat far. The last 1/4 "should" be 35 gallons. I'll bet it's more like 10, maybe less...
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