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Thread: Usable Fuel Capacity

  1. #1
    Member wildwill's Avatar
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    Default Usable Fuel Capacity

    I've been wondering this for quite some and just never got it figured out so finally decided to ask you wise folks. So I have a 2006 Seasport with twin 60 gallon--long skinny--tanks for a total of 120 gallons. That said, even after running one tank on empty for quite some time--like 35-40 minutes pecked completely on E the tank still only held a smidge over 48 gallons.

    So here is my question, did I likely have an empty 60 gallon tank that would only take 48 gallons, or still had 11+ gallons left and my fuel gauge is just that far off because of the placement of the float or whatever? And when I said it would only take 48 gallons that's it, anymore and it will puke out the vent on the side.

    Also, anyone have an idea how much fuel is left in these tanks before the pickup quits out? I would assume that at some point the pickup will stop working, but would bet with these long skinny tanks there is still some amount of fuel left.

    One of these days I will get brave enough to just run one of them dry and see.
    Since the World is 2/3 Water and Only 1/3 Land, Figures the Good Lord Intended I Fish More Than I Plow.

  2. #2

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    Your "fuel gauge is just that far off". I have never had any confidence in a float style fuel gauge - Never rely on it. I also have a Seasport with two 60gal saddle tanks. If you have original tanks - they are 60 gals. A couple of suggestions 1) get a fuel flow meter installed - night and day - takes the guess work out of it. 2) never run a tank dry unless it is an emergency. Who knows what you will suck up from the bottom of the tank - and what gets sucked will clog filters and/or ruin engines. I would guess there is less than a gal. when the pick up stops sucking and the engine starts coughing

    just my thoughts!

  3. #3
    Member Bullelkklr's Avatar
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    I wonder the same in my little searunner. Specs say it has a 52 gallon tank. Last summer I ran from Whittier out to the Needles. Stopped in blackstone on the way out and pulled pots and re-set them. Trucked on down through culross then out the bottom of knight and over. Stopped by the oyster farm on the way back after looking at some whales. Back into blackstone to pull the pots. Then back into port.

    I had an extra 7 gallons with me....thinking that I would need them. When I filled it up at the gas station in anchorage, she took on 45 gallons.

    So, by factory spec, I had 7 gallons left. How much was usable really I don't know. I was on empty at the oyster farm. I had one set of pots in culross that I dinked away some fuel on too. So - I ran 25 miles or so on empty and still had another 28 or so miles left........at least with my fuzzy math.

  4. #4
    Member Bullelkklr's Avatar
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    Also - what happens when you run one of these new 4 strokes out of fuel?

    Do the start right back up?

  5. #5
    Member spoiled one's Avatar
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    Quote Originally Posted by Bullelkklr View Post
    Also - what happens when you run one of these new 4 strokes out of fuel?

    Do the start right back up?
    I have run one of my tanks down to the point that the motors started to sputter a time or two. I immediately shut the motors down as I came off step, switched to one of the other tanks, and then reprimed the racor and motors. They have always fired right up. I would prefer not to do this, but sometimes it happens. After the two or three times that this has happened a quick glance at my fuel management gauge confirms that I am out on that tank. I have three tanks with independent fuel gauges that will show empty while I have about 20 gallons left. They are great for a quick check, but the FM guage is spot on.
    Spending my kids' inheritance with them, one adventure at a time.

  6. #6

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    Quote Originally Posted by Bullelkklr View Post
    Also - what happens when you run one of these new 4 strokes out of fuel?

    Do the start right back up?
    Yea they'll start right back up as long as the fuel line has only fuel in it and filters are not clogged.

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    Member Akgramps's Avatar
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    Quote Originally Posted by akroxy View Post
    never run a tank dry unless it is an emergency. Who knows what you will suck up from the bottom of the tank - and what gets sucked will clog filters and/or ruin engines.
    This is a interesting point that I have wondered about...if the suction is on the bottom of the tank, what is there to suck up that is not down there already.....? Water is heavier than fuel so it would already be at the bottom.

    Enough water would have to accumulate before the pickup would grab it....regardless of how much fuel is in the tank.....


    Jus wondering....
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  8. #8
    Member wildwill's Avatar
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    When we bought our boat two years ago (it's a 2006--so not original owner) one of the tank seals at filler neck was missing and had gathered a lot of water/condensation over the winter. I had the Volvo guy in homer drain both after I sucked up some crud and clogged the filter. Super cautious now--and missed the perfect opportunity to see how empty I could run them.

    Thanks for the info on the tanks Roxy.
    Since the World is 2/3 Water and Only 1/3 Land, Figures the Good Lord Intended I Fish More Than I Plow.

  9. #9
    Moderator Paul H's Avatar
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    Float fuel gauges aren't completely useless, but they are one reason for the rule of 1/3's. Invest in a fuel flow system, they aren't that expensive, are very accurate fuel gauges and will save you money by allowing you to fine tune your cruise speed.

    As far as running a 4s dry, they'll fire right up. I've had problems with my fuel system loosing prime and the engine cutting out. Re-prime, fire up and go.
    Those that are successful in Alaska are those who are flexible, and allow the reality of life in Alaska to shape their dreams, vs. trying to force their dreams on the reality of Alaska.

    If you have a tenuous grasp of reality, Alaska is not for you.

  10. #10
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    Our Bounty 257 has two 60-gal long skinny diesel tanks (although one of them is partitioned into 50 and 10, the 10 for kicker gas). The diesel fuel gauges are remarkably consistent, even if not strictly accurate, as long as we're level. On step they're way off, since the fuel gauge floats are in the aft end of the tanks and remaining fuel is tilted that way.

    We really wanted to know how much we had left at any point, so we paid particular attention to how many gallons it took to fill up, starting from a given tick on the gauge, and wrote these numbers down. After a few repetitions we had a very good idea of what any gauge reading really meant. Now I guess at each fillup how many gallons it will take, and often come within 1-2 gallons.

    We had done the same on our C-Dory 22, and it turned out to be really useful when stretching to cover some long distances.
    Richard Cook
    New Moon (Bounty 257)
    "Cruising in a Big Way"

  11. #11
    Moderator bkmail's Avatar
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    I ran my inboard out of gas once. I was too stubborn to pull over and dump the 10 gallons in that I was carrying. What resulted was a total pain in the arse. I then dumped in the 10 gallons but it didn't have enough head to prime the pump I think. She still would not start.
    Coast Guard Aux. pulled towed me from Pigot point to Whittier at a measly 2 mph or so.
    Filled the tank with fuel on the way home and she fired up instantly at home.
    A lesson learned the hard way and one I don't want to repeat.
    BK

  12. #12

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    Quote Originally Posted by wildwill View Post
    I've been wondering this for quite some and just never got it figured out so finally decided to ask you wise folks. So I have a 2006 Seasport with twin 60 gallon--long skinny--tanks for a total of 120 gallons. That said, even after running one tank on empty for quite some time--like 35-40 minutes pecked completely on E the tank still only held a smidge over 48 gallons.

    So here is my question, did I likely have an empty 60 gallon tank that would only take 48 gallons, or still had 11+ gallons left and my fuel gauge is just that far off because of the placement of the float or whatever? And when I said it would only take 48 gallons that's it, anymore and it will puke out the vent on the side.

    Also, anyone have an idea how much fuel is left in these tanks before the pickup quits out? I would assume that at some point the pickup will stop working, but would bet with these long skinny tanks there is still some amount of fuel left.

    One of these days I will get brave enough to just run one of them dry and see.
    When filling up my 2006 Seasport I found that gas would start coming out of the vents much sooner than the tanks were full. We always had someone holding a rag under the vent to catch gas so it wouldn't run down the side of the boat. After a few times I learned to listen to the "gurgling" coming from the vents and when I heard it then I'd slow down the flow of gas. I could usually put another 15 or so gallons in after that. The other "trick" that I figured out was to use the speed bump at my station and have the rear tire of my truck up on the speed bump so that the trailer was tipped just a bit higher at the front end. This also seemed to help to make sure the tank was actually full. Hope this helps...
    Ruby at the end of a good day.

  13. #13
    Member Bullelkklr's Avatar
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    Quote Originally Posted by Paul H View Post
    Float fuel gauges aren't completely useless, but they are one reason for the rule of 1/3's. Invest in a fuel flow system, they aren't that expensive, are very accurate fuel gauges and will save you money by allowing you to fine tune your cruise speed.

    As far as running a 4s dry, they'll fire right up. I've had problems with my fuel system loosing prime and the engine cutting out. Re-prime, fire up and go.

    I looked into the yamaha fuel management guages - they are $1200.00. Is there something aftermarket for fuel management on a yamaha that is "not that expensive"?

  14. #14
    Member joebut1985's Avatar
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    I don't have a seasport but the same thing has been happing to me. My gauge has been reading incorrect and I actually ran out of fuel because of it. I recently purchased a floscan that I will be installing this weekend and hopefully that solves my fuel gauge issues. My gauge has been reading less then what's in the tank and vise versa, so I will also be installing a new level sensor. I have found a company by the name of clean marine that supposedly offers a good fuel level sensor so I have been trying to get one from them. If I do get one I will let you know how there fuel level sensor works.

  15. #15
    Moderator Paul H's Avatar
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    Quote Originally Posted by Bullelkklr View Post
    I looked into the yamaha fuel management guages - they are $1200.00. Is there something aftermarket for fuel management on a yamaha that is "not that expensive"?
    Check out the lowrance LMF 400, it's plug and play with NMEA 2000 electronics and for most new engines you'll just need a wiring harness to connect it to the engine. Check BOE Marine, they have great pricing and will be able to tell you exactly what you need. Gauge and wiring harness should be under $300, if your engine won't talk to it, you can get a fuel flow sensor and gauge and sensor will be a bit under $400. If your gps is NMEA 2000 you can network it to the gauge and it'll give your mileage. If not, you'll get fuel burn in GPH and an accurate fuel gauge, but it's capable of alot more.
    Those that are successful in Alaska are those who are flexible, and allow the reality of life in Alaska to shape their dreams, vs. trying to force their dreams on the reality of Alaska.

    If you have a tenuous grasp of reality, Alaska is not for you.

  16. #16

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    I've been looking at the LMF 400 for a little while. My carbureted outboards won't talk to it though so I would need one of the paddle wheel sensors. Anyone know if the if Lowrance sensor is good? I would hate to have it clog/break while underway and deal with removing it.

  17. #17
    Member hoose35's Avatar
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    Quote Originally Posted by Kisutch View Post
    I've been looking at the LMF 400 for a little while. My carbureted outboards won't talk to it though so I would need one of the paddle wheel sensors. Anyone know if the if Lowrance sensor is good? I would hate to have it clog/break while underway and deal with removing it.
    Are you talking about the lowrance in line sensor, ep 60 i think? If you are, that is what i have been using for years with no issues and great accuracy

    Sent from my MB865 using Tapatalk 2
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  18. #18

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    yeah that's the one. Good to know it's accurate, thanks.

  19. #19

    Default Floscan

    Get one. About 300 bucks & a couple hours to install. You will recover that in fuel savings once you know your optimal burn (which changes depending on how the boat is loaded). Mine was used for a 2-sroke 150HP with carburetors.
    Not hard to install if yourself if you are mechanic savvy and not afraid to cut a hole in your helm.

    If you can connect an output to your GPS you can display mpg while you are running (I did not have this feature, but it would be nice).
    Get the re-settable totalizer option (manual switch to reset the total gallons burned).

    With A Floscan & tach I could tell if there was seaweed in my intake grate by the gauges before I could tell by a drop in performance.
    I knew within 2/10 of a gallon how much fuel I burned as confirmed when I fill up at the gas station.
    Can't imagine not having a Floscan (or other comparable) fuel burn gauge.
    It sure teaches you not to hammer the throttle because of graphic display about how burn rate doubles above about 80% max rpm.

    Tank float gauges are just rough indicators and not accurate enough if plan on cutting it anywhere close on fuel management.

  20. #20

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    Is there something aftermarket for fuel management on a yamaha that is "not that expensive"?
    Bullelkklr,

    I bought my Yamaha dual engine fuel management system off of ebay. Here is what I see out there right now:

    Dual Engine:
    http://www.ebay.com/itm/NEW-YAMAHA-D...#ht_1648wt_932

    Single Engine:

    http://www.ebay.com/itm/NEW-YAMAHA-D...#ht_1492wt_932

    If I remember correctly, I was able to get my dual engine system for around $400.

    Doug

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