How many of you suck off the bottom
+ Reply to Thread
Page 1 of 4 1 2 3 4 LastLast
Results 1 to 14 of 43

Thread:
How many of you suck off the bottom

  1. #1
    Half a bubble off jrork's Avatar
    Join Date
    Dec 2007
    Location
    Silverdale, Washington
    Posts
    2,467

    Default How many of you suck off the bottom



    I've pulled my two 8 gallon aluminum tanks and am going to get some new bungs welded on to try to improve my flow.

    I've searched till I'm sick of it and find that it's a bit of a 50/50 on who uses siphon tubes on the top and who uses pickups on the bottom.

    I'm switching to an electric pump and to me seems that it would be better to have it feed from the bottom but I would be interested in the pros vs. cons of an appropriately sized siphon tube versus a bottom feeding tank given the electric pump.

    Thanks

  2. Remove Advertisements
    PerformanceBoats.com
    Advertisements
     

  3. #2
    Senior Member
    Join Date
    Feb 2008
    Location
    Colorado Springs
    Posts
    436

    Default

    Mine are siphons but i think you can get just as much crap through the siphon as you can from a bottom feed. Wouldn't a bottom feed also push fuel to the pump on accelartion. A bottom feed should work better with filter between the tank and pump or switch valve than a siphon wouldn't it?
    Last edited by jungledave; 02-08-2009 at 09:12 AM. Reason: grammer

  4. #3
    Senior Member fleetimus's Avatar
    Join Date
    Dec 2007
    Location
    Colfax, Ca
    Posts
    1,260

    Default

    I use siphon tubes. Upgraded them to 1/2"

    Bottom bungs seem risky to me. If they cracked or broke at the bung, what will stop the gas leak???

  5. Remove Advertisements
    PerformanceBoats.com
    Advertisements
     

  6. #4
    Senior Member 4CE FED's Avatar
    Join Date
    May 2008
    Posts
    320

    Default

    Quote Originally Posted by fleetimus View Post
    I use siphon tubes. Upgraded them to 1/2"

    Bottom bungs seem risky to me. If they cracked or broke at the bung, what will stop the gas leak???
    X2

    ....My A1000 has no trouble pulling fuel out the top with -10 fittings

  7. #5
    Half a bubble off jrork's Avatar
    Join Date
    Dec 2007
    Location
    Silverdale, Washington
    Posts
    2,467

    Default

    JD and Tim, all good points and exactly the reason I posted this up for conversation.

    I can and would run a filter before the pump to keep from getting some crap in the pump and Tim, I share your concern though to be honest, a leak in the filter, a broken fitting on the pump or the pump failing could probably do the same thing.

    At the same time, it seems to me a fitting on the bottom of the tank would do a better job of keeping the electric pump primed. It that true or would a good siphon accomplish the same thing? Seems like I've read it both ways..

    Thoughts???

    Thanks guys.........john

  8. #6
    Half a bubble off jrork's Avatar
    Join Date
    Dec 2007
    Location
    Silverdale, Washington
    Posts
    2,467

    Default

    Whoops 4CE and I posted at the same time. Thanks

  9. #7
    Senior Member fleetimus's Avatar
    Join Date
    Dec 2007
    Location
    Colfax, Ca
    Posts
    1,260

    Default

    Granted, I am not running a blower. My Clay Smith works great feeding two 850s. I have -10 from tanks to filter, -10 to pump, -8 to regulator and -6 to carbs.

    Any leak after the tank can be stopped with shutdown. Leak at bottom of tank would not have any way to be stopped. JMO

  10. #8
    Senior Member Factory1's Avatar
    Join Date
    Oct 2008
    Posts
    1,134

    Default

    Siphon tubes are great if you are running mechanical pumps because the diaphram sucks and will self prime. Some electric pumps will not self prime, and that will just ruin an otherwise good day of boating. Second most siphon tubes are 3/8", 1/2 at best, fine for mild to mid level hp, may fall short for high end fuel pumps and motors. Also most high end pumps need a return line, theres another bung. As far as the thing breaking, I would shoot the welder if that happened. High quality welds are as strong as the base material, there is no need to worry about it. Second, that weld has near zero load or stress on it, very unlike say the welds on a v-drive strut. Here are some pics of a tank I just sold. I installed these bungs, 3/4" female national pipe thread (fnpt) supply bottom rear of tank, 1/2" return, top near fuel fill. As far as sucking junk from the tank, one you shouldn't be putting fuel with junk in it in your boat, two thats what filters are made for. Thats my 2 cents, but what the hell do I know?! Good Luck!!!
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	100_0703.jpg 
Views:	98 
Size:	89.1 KB 
ID:	32409   Click image for larger version. 

Name:	100_0704.jpg 
Views:	127 
Size:	91.1 KB 
ID:	32410  

  11. #9
    Senior Member 4CE FED's Avatar
    Join Date
    May 2008
    Posts
    320

    Default

    In my case, with the tanks already glassed in, it was quick and easy to thread an allen plug in the stock pickup.
    All that's left is to drill tanks and mount flanges/pickup tubes for the fittings.
    I draw off both tanks equally, and return to the separator.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	DSC00374.jpg 
Views:	117 
Size:	45.1 KB 
ID:	32411   Click image for larger version. 

Name:	DSC01195.jpg 
Views:	121 
Size:	95.5 KB 
ID:	32412  

  12. #10
    21 Daytona Outlaw's Avatar
    Join Date
    Dec 2007
    Location
    Artesia, N.M.
    Posts
    5,291

    Default

    Factory 1... you sure bring a lot of great advise
    for not knowing anything

    John, a fellow boater cured his fuel problems
    by adding a bottom pickup, works great no leaks.
    be sure to add a valve as close to the tank as possible
    for changing filters ect.

    On a different note, most are not worried about but
    its not coast guard approved
    #55

  13. #11
    www.highflowdynamics.com LakesOnly's Avatar
    Join Date
    Dec 2007
    Location
    San Francisco Bay Area
    Posts
    1,161

    Cool

    Quote Originally Posted by jrork View Post
    How many of you suck off the bottom
    I have, but she has to be amazingly, amazingly gorgeous and maintain very good hygiene.

    LO
    High Flow Dynamics
    Performance Components for the 429/460 Engine Family


    This post © Copyright 2007-2020 Paul Kane. No copying, linking, printing or otherwise without express written permission.

  14. #12
    www.highflowdynamics.com LakesOnly's Avatar
    Join Date
    Dec 2007
    Location
    San Francisco Bay Area
    Posts
    1,161

    Cool

    Quote Originally Posted by fleetimus View Post
    I use siphon tubes. Upgraded them to 1/2"

    Bottom bungs seem risky to me. If they cracked or broke at the bung, what will stop the gas leak???
    Bam, that's your answer right there.

    Jrork, if you want to increase "flow" then simply increase the diameter of your siphon tube/fuel line. How big you should go depends on the fuel requirements of your engine, as it is very possible to starve a high horsepower motor lean through the use of a fuel line that is too small and cannot deliver enough fuel to keep the engine happy.

    Going to a larger diameter fuel line also make it far easier for your pump to draw the fuel....try sucking milkshake through a straw, then try two straws...you get the idea. Double the diameter of a pipe and you increase it's capacity 4 times. [ pi(squared)r ] Going from 1/2-inch to 9/16-inch diameter, for example, increases the volumetric carrying capacity a whopping 24%. Not saying you need to go that big, it's just a figure I have on the top of my head due to some oiling caclulations, but it serves to give the picture how a slight increase in diameter makes for a big increase in fuel supply, pump works less hard, etc.

    LO

    p.s. Please forgive my post directly above this one, I suddenly thought I was on a different forum I frequent upon reading your initial question...
    Last edited by LakesOnly; 02-08-2009 at 10:30 AM.
    High Flow Dynamics
    Performance Components for the 429/460 Engine Family


    This post © Copyright 2007-2020 Paul Kane. No copying, linking, printing or otherwise without express written permission.

  15. #13
    Senior Member
    Join Date
    Dec 2007
    Location
    Concord, CA
    Posts
    939

    Default bottom feeders

    Don't suck off the bottom, but about 1" up the side. One would think this could keep any sediment out, but the way fuel sloshes, it would not matter. Think about it, on a siphon tube, its within 1" if the bottom as well.

    And Outlaw is correct, not Coast Gaurd approved.

    Jerry

  16. #14
    Half a bubble off jrork's Avatar
    Join Date
    Dec 2007
    Location
    Silverdale, Washington
    Posts
    2,467

    Default

    Lakes, I was kinda surpised that it took that long to get one of those kind of posts

    Thanks again everybody for the replies. I'm having a modest blown 502 built. Since this is a Gen VI block, electric is a must (don't want to go belt).

    I plan on going -10 for lines (currently -8) and will likely run a return (or at least have the bungs welded in for future) but have heard so many stories about the electrics losing their prime that I'm skeptical of a siphon tube.
    Last edited by jrork; 02-14-2009 at 07:42 AM.

+ Reply to Thread
Page 1 of 4 1 2 3 4 LastLast

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself.

Please select your insurance company (Optional)

Log-in

Tags for this Thread

Digg This Thread

Posting Permissions

  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts
  •  
 

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95