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How much gas is in your tank?


JT Quinta

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Two things that are absolutely unforgivable in boating. One is don’t drink and captain your vessel, EVER. The second is, know how much fuel you have in your boat’s tank. Gas gauges can be considerably off the true readings and this can be adjusted for by careful observation. Frankly, the only way to know really get that reading accurately is to compare your fuel gauge with the known amount of gas that you are filling up the tank with the boat in the water. So, I filled up my 21 MA with the known max tank capacity of  62 gallons. I knew my gas gauge was appreciably off the mark but how much, I simply was not sure. So, here are my numbers;  Yamaha gauge flashing 1 bar = 3 gallons of gas until stranded. 3 solid bars =13 gallons of gas. 5 solid bars = 23 gallon of gas. 7 out of 8 bars = 33 gallons of gas. After 40 gallons+ thru 62 gallons = 8 bars. So, my gas gauge is way off the mark but I now know what gas reserves I can count on in order to get back home. 

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3 hours ago, JT Quinta said:

Two things that are absolutely unforgivable in boating. One is don’t drink and captain your vessel, EVER. The second is, know how much fuel you have in your boat’s tank. Gas gauges can be considerably off the true readings and this can be adjusted for by careful observation. Frankly, the only way to know really get that reading accurately is to compare your fuel gauge with the known amount of gas that you are filling up the tank with the boat in the water. So, I filled up my 21 MA with the known max tank capacity of  62 gallons. I knew my gas gauge was appreciably off the mark but how much, I simply was not sure. So, here are my numbers;  Yamaha gauge flashing 1 bar = 3 gallons of gas until stranded. 3 solid bars =13 gallons of gas. 5 solid bars = 23 gallon of gas. 7 out of 8 bars = 33 gallons of gas. After 40 gallons+ thru 62 gallons = 8 bars. So, my gas gauge is way off the mark but I now know what gas reserves I can count on in order to get back home. 

Never rely on a gas gauge.....the only accurate way to know is a flow meter.

 

The only way to be sure is to calculate your mileage and reset the trip odometer based upon usage.

 

dc

 

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When I put in a new float for the gauge I drained my tank all the way.  That way I knew the amount at every bar like mentioned above.  I know when I start blinking low I have just over 10 gallons left. 90% of the time I add fuel at the house with jugs so I can easily keep track of fuel and check the function of the gauge.

I know some like to use their trip like Wanna but I rarely have the GPS on or would probably forget. Plus how do you calculate mileage if your GPS is on while using the troller?

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Of all the connections in previous boats the fuel sending unit required the most attention being buried in the hull and working on resistance, set the old senders up as close as possible small amount of corrosion develops on the open screw terminals and the resistance is off / fuel gauge off, like the new Yamaha gauge I believe 6YC  that shows gallons remaining/ used, one thing about the known flow of fuel ya know exactly what been used. 

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All systems have their shortcomings and need to be understood. Fuel gauges do not register in equal segments and need to be learned. Flow gauges tell you how much you have used, not how much you have. Basic math tells you that.(makes you wonder if new generation will need their flow gauge to come with a calculator).

The only true measurement is the dip stick.  But who is going to crawl into the console every 15 minutes. 

No matter the system knowledge and understanding is the important aspect of every part of your boat. Your safety and that of your passengers relies on that.

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2 hours ago, George Seither said:

True, Fish areas enough and you already have the insight of the average fuel burn for the trip, always fill up before you go. LOL on the calculator 

This here.  Always keep the tank full.  You never know when you are going to need it.  Its also better for the life of the tank.  Much harder to absorb water if the tank is full of fuel.  Also remember... What your gauge reads on trailer and in water are often different. 

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1 hour ago, Lap it Up said:

This here.  Always keep the tank full.  You never know when you are going to need it.  Its also better for the life of the tank.  Much harder to absorb water if the tank is full of fuel.  Also remember... What your gauge reads on trailer and in water are often different. 

Ditto....I fish within the same 30 miles to Lostmans out and 30 miles from there through the back 90% of the time....I have a 27 gallon tank, I get about 3.0-3.5 depending on the run...If I am planning on a longer day, I throw a 5 gallon tank in the bow for an extra 15 miles or so.

33*3=99 miles (60 rt) = my 1/3 1/3 1/3 rule....more or less.....

I think the issue is much more important if you are running offshore.....when i had my Dusky, some days I'd burn 100 gallons of fuel chasing Mahi if we were running and gunning and some days 30-50 if they were on the color change or in close....

I normally fill the boat once a week, the morning of the trip out at our local WAWA.

 

dc

 

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7 hours ago, mulligan said:

Plus how do you calculate mileage if your GPS is on while using the troller?

Mulligan,

Holy strong batteries on your troller.....how many miles are you trolling ???   3 miles is a long way on the 24V ......I don't  think it should be a major issue.

 

dc

 

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1 hour ago, Wanaflatsfish said:

Mulligan,

Holy strong batteries on your troller.....how many miles are you trolling ???   

My trolling motor is a tiller I deploy by hand so it can go further because I'm not spinning in circles:D.  In all seriousness there are many good methods that work.  I think the key is to be constant with what you do so the "oops" are cut out.  Fill it every time, use your trip, or whatever works for you and are comfortable with. 

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I had a engine data cable I got from BOE on the HPX. It plugs into the diagnostic port of the motor and displays on your GPS via NMEA 2000 network. Reads fuel flow to the injectors from the ECU, gives MPG, remaining fuel, burn rate, etc... as well as water temp, pressure, oil pressure, etc...

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10 hours ago, George Seither said:

Of all the connections in previous boats the fuel sending unit required the most attention being buried in the hull and working on resistance, set the old senders up as close as possible small amount of corrosion develops on the open screw terminals and the resistance is off / fuel gauge off, like the new Yamaha gauge I believe 6YC  that shows gallons remaining/ used, one thing about the known flow of fuel ya know exactly what been used. 

Yes, oxidation, terminal corrosion, wiring etc..., , resistance is the key. However, my rig is outfitted with a '06 HPDI 2 stroke so fuel flow metering is out of the question or too costly to consider. Distance traveled is relative to RPM's = speed I like to haul. Also, keeping the gas tank "topped off" with 62 gallons of fuel is insane not only because of the lethargic boat handling, pop to plane, draft etc..., the extra fuel  needed to push 500 additional pounds everywhere is measurable. My 21 is a cow with the tank full compared to when it is low on gas. In a perfect world that could work, for me, I have to look at the gauge hence my  measured explanation above. I don't know of any other way to guesstimate the fuel in the tank than to physically determine the readings on my gas gauge.  If anyone does it a better and more accurate way on older engines / rigs I'm all ears and appreciate your input.  

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13 hours ago, JT Quinta said:

keeping the gas tank "topped off" with 62 gallons of fuel is insane not only because of the lethargic boat handling, pop to plane, draft etc..., the extra fuel  needed to push 500 additional pounds everywhere is measurable. My 21 is a cow with the tank full compared to when it is low on gas.

If you had a Lake and Bay I would agree with you.  They don't react well to extra weight, but I'd say the 21 MA handles the extra weight extremely well.  I definitely wouldn't call 62 gallons "insane".  My little 2.6L carbed engine throws my boat around whether its full or empty.  The increase in draft is also very minimal. 

Draining your tank completely and then adding five gallons at a time and tracking what the bars on the gauge do is about the only way I can think of to guesstimate.  

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I use a very complex method to make sure I have fuel for the day.

full = full

Half= less than half

1/4= do not launch buy fuel 

  These calculations have worked on various sized tanks over the years. I have been stuck but I have not ran out of fuel once. 

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JT I'm with you about carrying around a bunch of extra fuel.  My typical trip is about 10 gallons of fuel.  I keep 15-20 gallons of fuel at my house.  When I get to half a tank or so I just throw 10-15 gallons in the boat.  It makes it easy for me to keep track of things and when I use the half tank as "time to add fuel" method there is always fuel in there if I make a long run somewhere.  I have never ran out or seen my gauge flashing, heck I'm not sure if I have been lower than two bars.

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Good post.  I ran out of gas on Tampa Bay just a couple weekends ago due to this exact issue.  Fuel gauge was reading full even though it was empty.  I couldn't remember if I had filled her up before I left so I didn't bother topping off.  Should've known better when I was pulling 2 extra mph at WOT.  Ended up getting a tow in from a fellow boater and paid him $120 cash.  A lot cheaper than $900 for SeaTow which I now have.  Also, having a handheld VHF was very very clutch.  I would recommend every inshore skiff have one.

I will always top off the tank before going out now.  I have replaced my fuel sender 3 times now and it has never really worked properly anyways.

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20 hours ago, JT Quinta said:

However, my rig is outfitted with a '06 HPDI 2 stroke so fuel flow metering is out of the question or too costly to consider

JT, Not sure who's GPS/Sonar your using but I'm reasonable sure 06HDPI Fuel Data is available from the engine, you might just need a engine data cable (Est $100) for which ever GPS/Sonar your using, look at the PDF below for what data can be picked up on the much older carb units the installation of a flow meter( EST $200) to a NEMA 2000 network get accurate Fuel flow to your desired device

Yamaha Engine NMEA2000 Connection.pdf

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6 hours ago, HoneyB said:

I use a very complex method to make sure I have fuel for the day.

full = full

Half= less than half

1/4= do not launch buy fuel 

  These calculations have worked on various sized tanks over the years. I have been stuck but I have not ran out of fuel once. 

Honey B and I use the same calculations...it ain’t rocket science....put gas in and go fishing....if you run 75 miles that day....put more gas in for the next day... my 2009 year 2200’s gas gauge is very accurate between 1/2 and FULL.....but, less than half....not so much. 

But.....half tank equals 30 gallons.....you can run over 100 miles on that.

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