Usable Fuel

Discussion in 'Downeast Boat General Discussion' started by WoundUpMarine, Jun 15, 2018.

  1. WoundUpMarine

    WoundUpMarine Captain

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    My buddy had the boat out the other day and "ran" out of fuel on his way back to the harbor. He didn't completely run out, but ran out of usable fuel while on plane, and idled back in. I have 2 - 150 gallon aluminum tanks, and after some measuring we figured out there is 30 gallons not usable per side, not sure if this is average or not, but 60 gallons total seems like a lot of fuel to be toting around never using. My fuel pick up is all the way forward, next to the forward bulkhead of the the tank. I'm thinking about getting an access plate and having a bung welded into it so I can move my pick up, thinking all the way aft. Or maybe 2/3's aft, what are you opinions?
     

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  2. Fishonnelsons

    Fishonnelsons Captain

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    Some believe the thought process of pick up being forward is this. Running at faster speed, fuel goes aft, pick up can get more fuel but using it up faster. When you go slower, "idle to the dock", tank is flat, forward pick up can get fuel as fuel is spread out, less fuel goes longer at slower speeds, forces you to putt putt back to dock slowly, conserving what you have.

    Or something like that!
     
  3. WoundUpMarine

    WoundUpMarine Captain

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    I had to read that twice, but get what you're saying, kind of like having the "reserve" function on an ATV. It would require you to "run" out of fuel going fast though, I don't like it. Definitely going to do something, just don't know if is better all the way aft or closer to 2/3's of the way aft.
     
  4. xbskt

    xbskt Captain

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    My Crowley has both forward and aft pickups and a crossover. After picking up some air one time in the Racor when below 1/2 I now run off the aft pickups and leave the crossover shut off.
    The aft pickups are pretty far back but not sure exactly. At least 3/4 if not more. I wonder why you would not go as far back as possible to maximize the upside of the usable fuel gained?
    I have pics on my laptop if you want them tonight.
    Let me know.
     
  5. fortier256

    fortier256 Captain

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    Maybe have 2 pickups forward and aft with a shut off on each. If you run out of fuel with the forward pickups, you could shut the forwards off and open the aft pickups and have a “reserve” supply. Of course you would have to keep the bow trimmed up in order to use the fuel.

    The real question is do you have enough usable fuel as it stands now to use the boat the way you want.

    I ran out of fuel when backing into my slip with the “new” boat. Pretty damn lucky I would say. The first thing that I did was stick the tanks. Now I know what my usable fuel really is. If I run out a second time it’s shame on me. Just sayin :)
     
  6. WoundUpMarine

    WoundUpMarine Captain

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    Having two pick-ups is a possibility, but I would much rather rely on monitoring my fuel tanks instead of "running" out of fuel before swapping to aft pickups, that will inevitably happen at the worst time, let along running your filters and pump dry. The boat holds 300 gallons, so I can hold more than enough for my needs, but the tanks are are too far aft and she squats pretty good when I'm full of fuel. I'd rather be able to run with half tanks when I can and use more of my total tank-age.
     
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  7. Henfruit

    Henfruit Senior Member

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    My pick ups are aft and at the bottom of the tanks (not up to todays standards) Novi built boat. Both feed to one fuel line to engine.
    Last fall last fill up revealed one tank was drawing down faster. May of had a blockage at the pick up? I hand the yard blow back both
    lines into the tanks and check the vent lines.I hope this solves the issue. Will know in a couple of weeks.
     
  8. chortle

    chortle Captain

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    I noodled the same questions you had about pick up placement. If in the back of the tank what happens when you are in big swells? Constantly going uphill then back downhill, the baffles in the tank are supposed to slow down any movement so in the middle makes sense to me for that case. If the water is flat and you are running on plane then it should accumulate in the back of the tank and you could suck it close to dry and then come off plane and in a few minutes or less the fuel levels out and you go dry sooner as the fuel sloshes around more quickly (less fuel being restrained by the small holes in the bottom of the baffles?) In any case, at this point you are way too low on fuel to begin with.

    I have aluminum tanks, shaped like a vee on one side at the bottom, the pick up is in the middle. With the old Cat that I had I ran out of fuel, once, the racor sucked bone dry, while on plane with the tanks showing 1/4 full. When back at the dock the tanks indicated 1/2 full. I changed the fuel level sender from an arm type to a vertical post/reed switch style and ordered the sender length such that when it showed empty I needed to get off plane and run flat which could then do for about 4 hours at 6 knots.
    [​IMG]
    [​IMG]
     
    Last edited: Jun 16, 2018
  9. WoundUpMarine

    WoundUpMarine Captain

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    The sloshing effect is what had me wondering if it would be worth having the pick up 2/3 or 3/4 of the way back. I guess this winter ill have to cut open a hole in my deck and see where the actual bafflers are to determine a place for the new pickup location. Even if I could get half of those 60 extra gallons it's another 2 hours at 20kts, way more if I pull the red lever back.
     
  10. leaky

    leaky Captain

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    Personally I get worried if I do not have 2X the fuel on board I might use for the trip I'm making - not possible for those who make long steams, but then you also leave the dock with full tanks and it's easier to keep track of what you've got.

    With two tanks it seems running out of fuel is 100% avoidable but another solution is to have a reserve tank someplace, even if that tank is just used to fill the primary tanks instead of being plumbed. I guess you could also just make two pickups, and have one be longer than the other too - so you actually run out when the tank gets below 1/3, if you really want a "reserve".

    The design problem which causes these headaches is when you make a long and shallow tank - that's the worst thing to have in a boat. Everyone wants the tanks below deck, space under the deck for other things, and a poop-ton of fuel, but if the space isn't really deep enough for it then you end up with a tank that allows picking up air even when it's still 1/3 full. Ideally a fuel tank in a boat should be more square - not much longer than it is deep, of course not the most practical thing, but if a tank is 1 foot deep and 6 feet long that's a really bad tank design where 1.5 feet deep and 4 feet long would be pretty good.

    Jon
     
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  11. WoundUpMarine

    WoundUpMarine Captain

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    My tanks are 5'7" long, 2ft'4" wide and 1' 7" deep, not ideal for length to depth ration. I still think using 2 pick-ups or a long and short pick-up are a bad idea, running out of fuel in general is a bad idea :) I wish my tanks were a few feet further forward, it would help with my running attitude and the boat wouldn't squat so much when they are full. So running the tanks at less capacity is my only realistic option.
     
  12. TCL

    TCL Senior Member

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    Since water and who knows what other sludge is sitting at the bottom of your tank, do you really want to use it at all?
     
    TCL,
  13. leaky

    leaky Captain

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    Well for the most part what you are picking up is from the bottom of the tank anyway - if you've got any water or significant sludge there is some important maintenance you've been avoiding.

    I think the bigger problem is if you run out of fuel with 20% of the tank left, that means you are sucking air well before that when the boat is rolling around, which can be a huge headache with diesels.
     
  14. Charlotte

    Charlotte Member

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    Both my current boat and previous boat drew fuel the aft inboard side of the tanks, about 1 inch up from the bottom.
     
  15. Diesel Jerry

    Diesel Jerry Captain

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    That is excessive. I would go with your plan but keep the pick-up space away from the bottom a couple inches (that's a guess). I would also add a pick up as close to the bottom as possible to "strip" your tank. It is a term and method I learned in the Navy, you may do it in your line of work. It gives you a provision to pull any water and sediment from the tank.
     
  16. Genius

    Genius Captain

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    May not be ABYC approved but one of my old steel tanks has a drain on the bottom. Love it.
     
  17. leaky

    leaky Captain

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    I think an access hatch and/or drain a diesel tank is a great feature - if it's not ABYC approved someone has their head up their ass, it is only diesel.
     
  18. Diesel Jerry

    Diesel Jerry Captain

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    Its either Coast Guard or ABYC. It's for two reasons fire safety and environmental. If the valve breaks of there is nothing stopping the fuel from pouring out. But you can do a low pick-up from the top.
     
  19. Kodiakan

    Kodiakan Senior Member

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    If you add a rear line I would leave my original in and valve it off just in case you want to go back to original setup. I’m guessing the pickup was placed there simply to have one access point. With the squatting you describe you probably couldn’t fill (all the way full) from the back, thus they put the lines forward
     
  20. WoundUpMarine

    WoundUpMarine Captain

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    I'm sure you're right that the pick ups were put forward for ease of access to everything. I've had the tanks cleaned so I'm not worried about sludge and water. The other think I like about putting one of those access hatches in is that you can get another spot into the tank to clean it.
     

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