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Fuel Tanks- Steel vs plastic

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  • Fuel Tanks- Steel vs plastic

    I have a fuel system problem / dilemma.

    I have large steel tank (120litres) (see photo before it was fitted by previous owner) for my force 70 and have had crud coming through to the inline filter killing the engine at high revs and collapsing the primer bulb. This crud seems to be of two types.
    1, brown/black possibly rusty stuff ? corosion of tank from damp air / water / pollutants in fuel
    2. small plugs of gum type stuff ? "sour fuel"

    obviously i need to clean the tank and fuel lines out but then what?

    my dilemma: do I
    1. keep tank as full as possible with fuel to reduce damp air above fuel and hence reduce tank corosion?
    2 keep tank running on low volumes fuel to ensure fuel turnover and prevent build up of gummy sour fuel

    or 3 just chop out the steel tank (which is glassed in under the floor of my boat and put in a new plastic one? (big job but tempting).

    any opinions on plastic vs steel tanks and tank sizes for normal day trips/skiing use would be appreciated.

    Attached Files

  • #2
    Re: Fuel Tanks- Steel vs plastic

    I think the plastic tanks may be your best bet to prevent moisture from corroding the tank. They are a bit pricey and they do expand, so that has to be taken into consideration.

    Have you looked at gas tank sealer? I know that some of the antique car enthusiasts use this type of product to preserve their original gas tanks. The kits contain several chemicals designed to remove any internal rust and inhibit any future corrosion.



    • #3
      Re: Fuel Tanks- Steel vs plastic

      That tank can be cleaned.Or it can be sealed.There is a tank sealer that coats everything in the tank and seals it in.This works best if the tank is out.
      You didn't mention the style of boat.Sometimes if your gonna do a repair like that it's easier to split the hulls and remove the tank(if you have a place to work.
      Plastic will work as good as the steel providing you install it correct.I put in a second tank under the console of my boat for longer ranges.
      To insure there is no more junk keep it full.Install a water/fuel seperator.J

      Buy American made Cars and Trucks!!!Towing insurance for a boat,a GREAT thing.

      In Scenic , Beautiful San Sebastian by the sea Florida

      88 Bayliner 21CC Twin 85hp Forces.


      • #4
        Re: Fuel Tanks- Steel vs plastic

        Thanks to both Jerry and PNWBoat,

        have included photo of my boat for your info. Fuel tank is located under the foredeck (ply then fibreglass then rubber sealant coating). Local expert diesel tank cleaning business owner reckons cleaning/sealant techniques only useful if you can make sure it coats entire tank...which I can't as i cant tip it/shake it around. Will be a big job to rip it out and put new tank in and will ruin the rubber deck and create potential leaks in hull liner.

        Plan at the moment therefore is:
        1. Empty the tank via fuel guage port and clean as much as possible (this hole is only 2inch wide.

        2. to buy the biggest plastic tote tank I can fit under the centre console and run new fuel lines and water separator filters to this.

        3. Go fishing. See if this system satisfies my needs.

        May eventually decide to take the plunge and put new tank up front.

        Still keen for any other ideas but at least this'll get me back out on the water safely.

        Attached Files


        • #5
          Re: Fuel Tanks- Steel vs plastic

          That is a double hull/The top and bottom can be split.LOT"S OF WORK!!!!!
          If you clean out the tank make sure no vacumes are used.
          Big tank under the console.The console can be removed to accomidate a bigger tank than you can stick thru the door.
          Make sure you put in a good filter system.Racor two stage with a sediment bowl.Fill out the profile so I can drop by and go fishing!!! J

          Buy American made Cars and Trucks!!!Towing insurance for a boat,a GREAT thing.

          In Scenic , Beautiful San Sebastian by the sea Florida

          88 Bayliner 21CC Twin 85hp Forces.


          • #6
            Sign up today
            Re: Fuel Tanks- Steel vs plastic

            Thanks Jerry,

            just a post FYI.

            Problem wth crud in tank turned out to be the sealant the last owner had used to seal the fuel sender to the tank instead of using a proper gasket. On siphoning off the tank I got horrible chunks of slimy sealant (10cm long!) out which were obviously choking the fuel outlet pipe.

            Have cleaned all fuel lines out but having been bitten once will be super conservative from now on. Am planning on still putting in a 20litre "emergency get home" tote tank under the console and conecting this permanently to my fuel line via a brass 3 way tap. This way if any more crud threatens the filters I can just switch to a known pure fuel supply and cruise home.

            Thanks for all your advice.

            Oh and if you're ever NZ look me up for a fish!