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Thread in 'Motors & Props' started by Mike Ratko, Jul 25, 2014.

  1. Mike Ratko

    Mike Ratko Well-Known Member

    Likes Received:
    Feb 12, 2005
    Montreal, Quebec, Canada
    If you are having or had fuel issues with your Optimax, you probably have read about the fuel regulator and how it is not serviceable and Mercury would have you order a new port fuel rail for somewhere between $1200-1600. There are a couple places that will “service” your fuel rail for prices ranging from $380 to $950 and for that price you will magically get a new fuel regulator diaphragm.

    I was all set to send my fuel rail to Florida for a new fuel regulator when I read a post on a couple of forums from a user called OKByMe. In a few lines he described his procedure to rebuild the fuel regulator diaphragm assembly with the rubber diaphragm from a tracker valve. I PM’d him for a bit of clarification and then set to work to duplicate his efforts. And it works! I was able to rebuild my fuel regulator diaphragm assembly and get the motor back to running condition at factory specs for fuel and air pressures. Here are the detailed steps to rebuild the fuel regulator diaphragm assembly.

    First let me clarify the terminology I will use. When I refer to the ‘fuel regulator assembly’, I am talking about the rubber diaphragm itself and the metal ‘core’. Together they are the ‘assembly’. The fuel regulator diaphragm is the piece of rubber. My original fuel regulator diaphragm was turquoise (see photo). The new one is purple.

    The rubber diaphragm of the tracker valve on the starboard fuel rail is EXACTLY the same as the rubber diaphragm of the fuel regulator. The only difference between the assemblies is the metal core. One metal core does work in both. The metal cores must be disassembled to remove and replace the rubber diaphragm.

    Secondly, here are some DO’s and DON’Ts that I highly recommend you pay close attention to:
    DO – disconnect the negative terminal of the battery
    DO – remove lower cowling before trying to remove fuel rails
    DO – remove fuel rails from studs
    DO – remove all fuel, water, and air lines
    DO – use anti-seize compound on the screws when reassembling
    DO – use a torque wrench when tightening screws and nuts
    DO – torque screws to a maximum of 70 in lbs
    DO – torque fuel rail studs to 33 ft lbs
    DO – check all connections and covers for fuel leaks when the engine is running
    DO – fix all fuel leaks IMMEDIATELY. TAKE NO CHANCES.
    DON’T – over tighten screws – even if using a torque wrench
    DON’T – attempt to service the diaphragm while fuel rails are mounted on engine (that is how I got in this mess in the first place)
    DSC01007 (640x360).jpg

    I got the new rubber diaphragm from a new tracker valve. I needed one tracker valve because mine was torn (after 12 years of wot runs) and I ordered a second to repair the fuel regulator diaphragm. I removed the diaphragm from the tracker valve the same way I removed it from the fuel regulator diaphragm assembly.
    DSC01044 (640x360).jpg

    DSC01045 (640x360).jpg

    To disassemble the cores, I made a tool to fit in the groove of the fuel regulator diaphragm core. I used a 10mm socket and opened up the inside diameter to clear the round ‘bearing’ in the center of the core, and shaved the outside to fit inside the flange or ‘swedge’ of the core. I used a grinding stone in a dremel-type tool to grind the inside diameter and a file for the outside diameter. I shaved the outside of the socket high enough to accommodate the wrench I used to squeeze the swedge. I mounted the socket in a drill (or you can use a drill press) to help hold the socket and increase the apparent rpms of the grinding tool. I made this tool to prevent the swedge from folding in while I squeezed the swedge to a vertical position. I am not totally sure you need this tool but I am sure according to Murphy’s law that if I didn’t take the 20 minutes to make it, something would have happened to make me want to have it. The same tool can be used to open the swedge on the new tracker valve.
    DSC01026 (640x360).jpg

    The swedge is holding down a flat metal washer on top of the rubber diaphragm. By straightening out the swedge, you will be able to remove the washer and the rubber diaphragm. I used a 6” Bionic Wrench from LoggerHead Tools to straighten the swedge. It is a six-sided wrench that you squeeze like channel-locks.
    DSC01017 (640x360).jpg

    DSC01021 (640x360).jpg
    You can use a collet of some type like a drill chuck, or pliers that are very flat on the side. There is not a lot of material to grip so you don’t want to use a tool that has rounded edges. By rotating the diaphragm assembly and squeezing firmly but not too much, in a few rotations I had the swedge straightened up enough to remove the washer. Remember you are working with stainless so you need a bit more strength than for mild steel and the stainless is much less forgiving if you do not have the swedge vertical enough.

    DSC01027 (640x360).jpg
    Once the washer is off, replacing the rubber diaphragm is a snap. Then you replace the washer and using a different tool, you bend the swedge back in place to hold the washer. The second tool you will need is another 10mm socket. Grind out the inside diameter to clear the center bearing, then chamfer the outside to 45°. I then placed the tool in the proper location and put the tool and diaphragm assembly in a 4” vise and squeezed everything into place.

    DSC01015 (640x360).jpg

    I made sure that the swedge was bent the right amount by comparing the original height of the assembly at the swedge to the ‘repaired’ height. The washer sits on a shoulder on the core and ensures a perfect fit to the rubber diaphragm.

    IMG_20140712_184944 (640x360).jpg
    After I reassembled the fuel rails and mounted them on the engine, I primed the fuel system according the owner’s manual and then cranked the engine. In about three seconds it was purring like she was brand new. I checked the fuel and air pressures on the port fuel rail and everything was in spec. I shut down the engine and waited 20 minutes to restart it. When I did, it fired and purred smoothly.

    As far as I am concerned, I saved at least $300 and probably more. I hope this post helps someone else in a similar situation. At the very least, know where I can find the instructions if I need to help someone work on their boat ;^)


    2002 Nitro NX882DC with 175 Opti
    AirForce likes this.
  2. AirForce

    AirForce Well-Known Member

    Likes Received:
    Apr 17, 2013
    Smyrna TN
    Mike, that's a good writeup and I love documentation on people do things. Kinda like a detailed OEM Service Manual.
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