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Tankage and usable fuel

Discussion in 'Engines' started by Capt Ralph, Mar 8, 2023.

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  1. Capt Ralph

    Capt Ralph Senior Member

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    Based on an other thread regarding fuel tank sizes and usable fuel.
    I started thinking about usable in a tank.

    I wondered how much of these big numbers is usable fuel.

    Always bugged me that the mains fuel pickup is not on the bottom.
    If there is gunk on the bottom of the tank, would you not want that picked up and filtered?
    In rough water, it will get picked up,, at the wrong time.
    I had my pickups up years ago chasing another problem.
    aft tank fuel pick-up 002.jpg
    Next time available, I'm extending mains pick ups to the bottom.

    Don't we want to filter all the stuff in our fuel tanks? Before it gets mixed up at the wrong time?

    Potable water is from the bottom to ensure all is fresh?
    Don't we want all fresh fuel in our tanks?

    When possible with separate pick ups, gen-sets are always up higher. Nice to have a reminder your Bingo in case you really mess up.

    Why am I working (again) against the standard way things are done??
    sorry_smiley_20150321_1500256250_c33646972fa7e3a8d9fe3eb86cc9016c1150a4e3.png
  2. cleanslate

    cleanslate Senior Member

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    Hmmm.. I don’t know if that’s a good idea CR. Our Detroit’s can take a lot of fuel abuse. Never had mine shut down due to fuel snot, which I’ve had plenty of.
    It always shut down my skinny fuel line in rough weather on my Generator , but it’s pretty good now after multiple seasons and many sporty trips about .
    My larger Detroit mains large fuel lines with the large Racors etc filtered things out very well. I’ve always got home with no shut down .
    Not a great idea to suck up stuff from the very bottom of the tank.
    When are you ever going to get the fuel that low ?!?

    Did your Detroit mains ever shut down on you because of clogged , snotty filters?
    I bet no.

    Let it be as Sir Paul would say.
  3. Capt Ralph

    Capt Ralph Senior Member

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    But now I know my tanks are clean now.
    WITH, unused fuel below collecting stuff again.
    I want the filter it all. Then, no more stuff in my tanks.
  4. cleanslate

    cleanslate Senior Member

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    IMO, you have to run the boat every day to achieve totally purity.
    Did your mains ever shut down due to clogged fuel plumbing?

    Yes or no CR ?
  5. Capt Ralph

    Capt Ralph Senior Member

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    No.
    You see that pick up screen, we still ran.
  6. cleanslate

    cleanslate Senior Member

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    Yes , that’s my point. 71s rule.
    I’d say you’ve got a better hand on it since that photo.

    Let it be.

    Something else is lurking around the corner waiting to break. Save your energy for that.
    Start em up, throw the lines and take her out for a run, where ever it be.
  7. leeky

    leeky Senior Member

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    Isn't that what fuel polishing systems are for?
  8. Capt Ralph

    Capt Ralph Senior Member

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    It's just the thought of another hundred gallons (per tank) that does not get picked up on our Bert.
    I want that to be good usable fuel.
    I'f I'm Bingo mains fuel, I would go crazy knowing, while drifting, There is really another 1 or 2 hundred gallons of fuel down there.
  9. Capt Ralph

    Capt Ralph Senior Member

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    That is why now,,, I know the fuel in the tank bottoms is good. I did fix that stuff problem from years ago.
    Just don't want to grow another stuff farm under my pick-ups now. Filter it all.
  10. cleanslate

    cleanslate Senior Member

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    Lol, marketing nonsense.
    You’ve got to run the vessel, use fuel.
    If they sit for long periods of time, no polishing system is going to work.
    Other than the Racor filters and the secondary engine factory filters.
  11. Capt Ralph

    Capt Ralph Senior Member

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    But if there is fuel under your pick ups, it never gets filtered.
    Stuff is heavier than diesel.
    Use the boat yes, Hit that choppy weather and that bottom stuff gets picked up at the wrong time.

    Maybe I'm typing all of this wrong??
    Are you kids understanding that the stuff under the pick up that never gets cycled? or used?
  12. rtrafford

    rtrafford Senior Member

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    I agree with the thought process, CR. I think my answer would be to have a fuel polish/transfer system that pulls that unreachable fuel for cleansing as well as the ability to transfer it to another tank where it can be used. Three tanks on board here combines for likely 150 gallons of fuel beyond reach. When I transfer fuel at sea, I'll stop with half a tank moved to allow the rest to churn before I move it. I'm running it through the filtration set up for polishing, and I want all aliens removed, if possible, from the tanks. That's just a dedicated second pickup to be used by the transfer/polish system. With that in hand, more than half of that unreachable fuel can be accessed for the systems.
  13. DOCKMASTER

    DOCKMASTER Senior Member

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    I also hate the inaccuracy of the fuel gauges. I realize it's near impossible to get accuracy given the angle of the tanks changes with the attitude the boat is running. My fuel gauges start to read near the empty mark with boat sitting level as a pass half fuel used. At normal cruise which has the bow fairly high, they read better but still off a ways. The fuel senders are all in the aft side of the tanks given the fuel runs aft when bow is up at cruise. The only good thing is my new CAT's have a pretty accurate fuel used reading so as long as I remember to reset when taking fuel I've got a better sense of what I've used. Of course, this doesn't account for gen fuel but that's pretty minor.

    My engine room tanks sit higher than my cockpit tank. In a pinch I could align the tanks such that the engine room tanks would gravity feed back to the cockpit tank. But this would still only allow the tanks to be drawn down to the where the pick up tube ran dry.
  14. Capt Ralph

    Capt Ralph Senior Member

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    DM reminds me of another "Got-Ya" I have to deal with on our boat:
    The aft tank bottom shape is deeper, at it's forward end, following the contour of the hull from the transom forward.
    The fuel pickup is at the aft end. When the boat is level or idling at hull speed, there is probably another hundred gallons unusable.

    Aft tank fuel level sender in near the middle (for/aft) of the tank, when the bow does go up, tank level goes up.
  15. Capt Ralph

    Capt Ralph Senior Member

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    My Fix
    You kids remember old motor bikes. The fuel valve; Off, On, Reserve..
    I'll send down a second main engine pickup. Towards the front of the aft tank also. Rite to the bottom with an angle cut.
    With a valve, used for fuel polishing and fuel reserve.
  16. Capt J

    Capt J Senior Member

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    The pick ups need to be 1" above the bottom to allow the fuel to flow to the pickup. Put a shopvac end in water in a bucket, then put it close to the bottom of the bucket, if you get too close it causes a vaccuum which sucks the end to the bottom of the tank.
    yr2030 likes this.
  17. Capt Ralph

    Capt Ralph Senior Member

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    My dearest Skippy J, Your comments are most interesting and welcome most times.
    On this topic, we are discussing our 45 year old Bertram with rather solid fiberglass fuel tanks.
    This is not a tin can fuel cell built to Carver spec.
    Also, If you didn't notice in post #15? Angle cut on the pick up.
  18. Capt J

    Capt J Senior Member

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    I think the angle cut will make it suck air sooner with the fuel at a higher level. Every tank pickup I've seen has been flat at the bottom and usually 1" above the tank bottom, for a reason.
  19. SplashFl

    SplashFl Active Member

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    On a tank related subject. According to the part time captain, the original owner always ran off the aft tank. During removal of the forward tanks sending unit I learned that tank was full so I switched the two engine fuel valves to run off the forward tank and in just a few minutes the starboard motor stalled and would not start. After switching that motor's valve back to aft tank she fired up and ran fine so what can be the issue? Generator only feeds off the aft tank.
  20. Capt J

    Capt J Senior Member

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    Either you have it valved to off instead of the foward tank (which is what it sounds like). Or the fuel line is collapsing or clogged.