Fuel Issue

Discussion in 'Downeast Boat NEWBIES' started by YankeeClipper, Jul 6, 2018.

  1. YankeeClipper

    YankeeClipper Member

    Oct 1, 2016
    Likes Received:
    Boat Make:
    32' Osmond Beal
    So I'm a rookie, but reading alot, and trying to learn.

    Cummins 6BTA, 400 hours, recon 2007.

    You guys helped me out when I posted 2 weeks ago about OVERHEATing.

    Since overheating a lot has been done. Hired a Cummins/boat mechanic. Raw water system serviced: flushed, barnacle buster, strainers checked, impellar changed, coolant changed, hoses changed. Alarm working fine. Tach checked, propped close to ok; engine rated at 3000 rpm, turning 3060.

    Here's my new dilemma.

    Running at 2100 RPM, and engine stalled. Two 120 gallon fuel tanks, each half full at start of trip; by dipstick. Fuel filter had been changed. Somehow air got into the fuel lines. I primed the lines and was able to restart engine. ran fine for a while, but then stalled again. Reprimed, fine.

    Checked fuel tanks; starboard tank almost full, port tank 1/8 full. Shut port tank valves off, and ran fine into dock.

  2. OLD BAY

    OLD BAY Captain

    Aug 25, 2012
    Likes Received:
    Annapolis, Md
    Boat Make:
    Wasque 32
    Sorry to hear about your fuel troubles.

    Were you running on both tanks, or that port tank? Sounds like you were pulling air from that port tank and that 1/8th of a tank may be your level for unusable fuel.

    Others with more knowledge will chime in.
  3. Fishonnelsons

    Fishonnelsons Captain

    Sep 14, 2015
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    Charter boat Captain
    Truro, Cape Cod
    Home Page:
    Boat Make:
    38 Wesmac
    Issues with your lines. Need to know how your lines are set up. Probably you have a supply line from each tank going to one valve to one supply line to the engine, and one return line from engine going to a valve and then a return line to each tank.

    Two ways to run. Sometimes it's set up so you can run off both tanks simultaneously. System draws from both tanks and returns to both tanks simultaneously. Levels in each tank stay relatively the same. Easy this way. HOWEVER issues may arise. Air leak in any of tank hoses, clamps etc will cause an imbalance in flow and return, creating what you describe. Also, from experience, when tanks are half or less, and you rock and roll a bit, a pickup in one of the tanks may suck air versus fuel once or twice resulting in only one tank being active. I had this setup in a 28 and it happened to me a few times, then I had to fool with the return and supply lines. Turn supply to full tank, return to emptier tank, monitor til about equal etc.

    New boat has same number of lines but valves are setup so I cannot run off both tanks, only one or the other. So I run 3-4 short trips, then flip my valves. Have to keep track of it and monitor or else the unevenness of thebtanks and their weight unbalances the vessel. Coming up from Florida we would run five hours on one tank, then switch and run the next on the other tank.

    While I can't run off both tanks at the same time, my valves are such that I can run supply from one and return to the other, and vice versa. Good if one tank is out of balance because I forgot to switch, bad if the valves get mixed up and I over return to one tank and overflow it, speaking from experience again.

    First thing I would do is trace my tank lines to identify and label them perfectly. Port return and supply, starboard return and supply. Then tighten up all hose connections everywhere in fuel system. Obviously fill up both tanks close to max, but not quite. Then run with supply and return hose to one tank for 2 trips. Check fuel level to ensure used tank going down correctly and unused tank staying where it stated. Switch to second tank and do the same. Prove that at least you can run off either or tank. The with tanks full again, after you have labeled lines and tightened clamps, run off both fir 2-3 trips. Check fuel levels to see if both tanks came down relatively equal.

    Hopefully with all that the issue is fixed, if not, you have enough data to determine where problem lies. Leaky fuel line, faulty valve, etc.

    My gut is you created a vacuum in one of the pickups and your supply and returns got screwed up, you were using from port and returning to starboard. I always get fuel when I'm halfway down my tanks just to avert this. Or, somehow the valves got moved to the wrong position and you were using port and returning to starboard. Easy fix there.
  4. Snake8

    Snake8 Member

    Dec 1, 2016
    Likes Received:
    Do you have a secondary fuel filter other than the one on the engine? A Parker/Racor?

    Agree w fishonelsons. Trace and label all your fuel lines, isolate the problem. Its probably an easy fix. Also dont neglect the tank vent(s) it should relive pressure as well as vacuum.
  5. IfishHard718

    IfishHard718 Member

    Feb 8, 2016
    Likes Received:
    Brooklyn NY
    Boat Make:
    31 Duffy
    I also agree with Fishonnelsons! Seems like your return valve is open to the larger tank. So ultimately your supplying fuel from one tank and whatever isn't used is returning to the other.( this drains the tank quicker) I personally also have two tanks and the way I avoid this is by using one tank at a time. I fill both tanks fully. One tank is a little larger than the other so I open both the SUPPLY AND RETURN on the Port tank leaving the supply and return on starboard tank closed. When the tank I am running off reaches quarter tank (never wanna run too low...rough seas u can suck up air causing stall or your sucking in all the crud from the bottom of your tank) I open the valves on the other (full tank) tank and SHUT both RETURN AND SUPPLY on the one I was running off. Good luck!

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