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New member to group. Purchased Yamaha 25hp 4 strk, F.I. motor and have questions

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  • New member to group. Purchased Yamaha 25hp 4 strk, F.I. motor and have questions

    Just bought new Yamaha from Houston boat show. Won't get it for another week. Does this motor require a vented or non-vented fuel tank? A tech at boat show said he highly recommended a 10 micron water separator between engine and tank? I have easy access to ethanol-free gasoline. Do I need one? And if so, can anyone recommend one? After a day on the water, what is the procedure for draining all fuel in motor? I am used to old carburetor models. Thanks in advance.

  • #2
    Welcome to the forum. Congratulations on the purchase of the new Yamaha.

    First, the tank. The motor neither knows nor cares where its fuel comes from. It is the EPA that cares. So, if you have an older vented directly to the atmosphere tank it will work just fine. You might need to install a new style fitting at the motor end. On the other hand, if a tank came with the motor it will be the newer Yamaha style that is also vented but with pressure control mechanisms built into it. They can be somewhat problematic. The tank may swell up like a balloon during the day when out in the sun.

    The tech that recommended an additional fuel filter is erring on the side of caution. Maybe 99% of motors owners don't need a supplemental fuel filter. But it cannot be known who the 1% are that needs them so the suggestion is that everyone use one. Better safe than sorry or a waste of money? That is for each to decide on their own. I am partial to the Racor style with the clear plastic bowl at the bottom so that the gasoline can be monitored for the presence of debris and/or water that gets to the fuel filter.

    In an EFI model it is more difficult to drain the motor of gasoline. Most don't/won't be doing this. If the motor is used frequently and clean, fresh gasoline is used then there is little need to drain it. The system is sealed whereas a carburetted model is not.

    Lots of folks with carburetted motors run them dry. Not recommended in an EFI model. It could damage an expensive electric fuel pump.
    Last edited by boscoe99; 01-11-2018, 02:27 PM.


    • #3
      Yamaha makes and has these for sale on this parts site. Sierra, Racor or some other brands. Some like the type that has a clear bottom section that can be seen to show if any water etc has go the in the fuel and to drain. I don't believe Ymaha's are that way, mine is not. I simply change mine every six months and after bringing out of winter storage. There are two Yamaha types a mini separator and a regular size one. I would even with non ethanol gas use a stabilizer just for S&G especially if you don't drain the tank each use. Not sure about draining fuel out of the engine? I have not heard of that with a four stroke but I am sure there may be some opinions? I run my F115 at least weekly and have not drained fuel, but use both Yamaha ring free and Stabil Marine all the time with no problems.
      Keep life simple, eat, sleep, fish, repeat!


      • #4
        FI'ed engines have no where's near the issues like a carb, varnishing up with old fuel... Different beast..

        Agreed on the additional fuel filter with the see thru base (you can see/drain water easily). Cheap insurance..

        I'd also use a fuel stabilizer (Gas Shok" is very good IME) unless you run the tank dry. Again, with the FI, NOT nearly as critical..

        The see thru, spin on filter:


        • #5
          Thanks to all for your prompt replies regarding the fuel tank, fuel filter, and fuel stabilizer. Y'all were basically confirming for me what I have been thinking myself. I am a retired mechanic and shop teacher who still messes around with drag racing, so I have some mechanical knowledge. Outboards have made such drastic changes over the years that I thought I would seek expert advice from end users. Thanks again for your input.