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Fuel tanks and return valves on diesels? i know this has been up before....-gctid397134

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    Fuel tanks and return valves on diesels? i know this has been up before....-gctid397134

    But I still don┬┤t get it...and cannot find the old thread.

    I got 34 Fj Trophy -89 with twin Hinos. Forward tank 190gal, rear 129 gal. The valves are set so that port engine takes fuel from the rear (smaller tank) and stbd from the forward tank. BUT, when cruising, the rear tank fuel level harly drops as the forward goes down much faster. I looks like the return hose from both engines goes to the rear tank as it got 2 + 5 hoses connected to it ( Fuel fill + air, diesel gen pickup and return, port pick up and return, stbd return)? Fwd tank got 4 connections: Fuel fill + air, stbd and port pick up? Or should it also have a return somewhere that i cannot find?

    -Can this be right?

    -How do you recommend to put the valves? To connect both engines to the rear tank (pick up & return) and leave forward unused? Or how can i get them balanced?

    Thanks

    Mag

    #2
    You are going to need to trace both the fill and ther return hoses from both engines to the valve bank and then to the tanks.

    Mark each valve and each position on the valve as to its function.

    Then you'll know how your valves are setup. Do not count on them being "factory stock".

    This will probably take an hour or two to do, but once you have your system documented, it'll make fuel managment much easier.

    KEVIN SANDERS
    4788 LISAS WAY - SEWARD ALASKA
    www.transferswitch4less.com

    Whats the weather like on our boat
    https://www.weatherlink.com/embeddab...59665f4e4/wide


    Where are we right now? https://maps.findmespot.com/s/36S4

    Comment


      #3
      Sorry for this long posting but

      Thanks Kevin. I checked now all the valves, fuelines and the set up and connections/instllations are as follows: the port engine takes fuel from the front tank (190gal) and returns to the aft (129gal) tank. The stb engine does the opposite; takes from rear and return to front. The returns are fixed and cannot be changed, but there are valves that can be adjusted from which tank to take the fuel. I am thinking of changing so both engines takes fuel and returns it to the same tank it draws fuel from.

      Q1:Can this be done without having to bleed/air the fuelsystem? Like right now?

      Q2: The big guestion: for some reason the fuel level in the aft tank hardly drops at all after several hours of driving but the front (190gal) drops so that after 130nm it is almost empty! (it should not be even halfempty)I have looked all over and cannot see that there would be any direct connections between the tanks that would even them out or anything. Also no leaks anywere. I also suspected the engine tuning is wrong, but both engines run fine, normal heat, no extra smoke etc. at cruising 2600rpm and 18-19 knots. Or can an engine be so out of tune that it┬┤s fuel consumpiton triples? Earl?

      The boat used to have a diesel generator which we remowed years ago, so there are valves left, to both tanks that are closed. Could this or its returns interfear somehow with this? I cannot se how?

      I filled up the tanks so to check their accurancy and cauges and they are OK.

      But something is clearly wrong. All ideas are welcome, please.

      thanks

      Mag

      Comment


        #4
        Unless you are purposely trying to rebalance tank levels ALWAYS have one engine drawing on a single tank and returning excess fuel to the same tank. If you do not do this, you can overfill a tank and start pumping fuel out your vent. This has happened to a couple of friends that did not do this with their gen set and found themselves complaining about the fuel spill on the water, that turned out to be all their fault.
        Started boating 1965
        Bayliners owned: 26 Victoria, 28 Bounty, 32, 38, and 47 since 1996

        Comment


          #5
          mmichellich wrote:
          Unless you are purposely trying to rebalance tank levels ALWAYS have one engine drawing on a single tank and returning excess fuel to the same tank. If you do not do this, you can overfill a tank and start pumping fuel out your vent. This has happened to a couple of friends that did not do this with their gen set and found themselves complaining about the fuel spill on the water, that turned out to be all their fault.
          Exactly!

          The OP needs to put valving in the return line so that he can return the fuel to the same tank he took it from.

          anything else is asking for a disaster.

          KEVIN SANDERS
          4788 LISAS WAY - SEWARD ALASKA
          www.transferswitch4less.com

          Whats the weather like on our boat
          https://www.weatherlink.com/embeddab...59665f4e4/wide


          Where are we right now? https://maps.findmespot.com/s/36S4

          Comment


            #6
            Thanks for the replies.

            Just to be sure, I can then adjust the valves now without the risk of the engines getting air or stalling? I will make them draw fuel from same tank it returns to.

            Sorry for asking but what is "OP"? English is not my native language as you can see from my posts.

            Thanks again.

            Mag

            Comment


              #7
              Mag535 wrote:


              Sorry for asking but what is "OP"? English is not my native language as you can see from my posts.

              Thanks again.

              Mag
              No problem, short for "Previous Owner"

              Comment


                #8
                Mag535 wrote:
                Thanks for the replies.

                Just to be sure, I can then adjust the valves now without the risk of the engines getting air or stalling? I will make them draw fuel from same tank it returns to.

                Sorry for asking but what is "OP"? English is not my native language as you can see from my posts.

                Thanks again.

                Mag
                OP stands for the "original Poster" in this case you. You started the thread asking a question. You are the OP

                KEVIN SANDERS
                4788 LISAS WAY - SEWARD ALASKA
                www.transferswitch4less.com

                Whats the weather like on our boat
                https://www.weatherlink.com/embeddab...59665f4e4/wide


                Where are we right now? https://maps.findmespot.com/s/36S4

                Comment


                  #9
                  Mine has two 350 gallon tanks that are connected at a lowpoint with a 1" line that allows me to very quickly re-balance tanks. This is opened when I polish from one tank to the other. It's also useful when I want to drain one of my water tanks. Simply fill only the water tank needed to trim the boat and then close that low-point transfer. Then the weight of the fuel keep the boat level trimmed. My water is setup the way. It's pretty handy.
                  Custom CNC Design And Dash Panels

                  iBoatNW

                  1980 CHB Europa 42 Trawler- "Honey Badger"

                  Comment


                    #10
                    Thanks Kevin & Co.

                    They now draw from same tank as returning to. Seems to be working as fuel is drawn from both tanks now.

                    However, I still feel the port engine uses much too much fuel. How can this be checked? My calculations are that at 2600-2700 rpm and 18-19 knots not more than 1gal / naut.mile should be consumend by both engines together.

                    Any thought on this?

                    Mag

                    Comment


                      #11
                      That actually seems a bit low (1gal/mile) on a planing twin at 18 knots?
                      Custom CNC Design And Dash Panels

                      iBoatNW

                      1980 CHB Europa 42 Trawler- "Honey Badger"

                      Comment

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