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F75 to F90.... a new angle

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  • F75 to F90.... a new angle

    I know horsepower can not be made out of thin air.... However it can be made out of thin air and a smidge more fuel. If one where to remove the restrictor more fuel must be added. that's where the 800$ ecu or 300$ fuel programmer come in, or are they really needed?

    This summer I picked up a 2004 Suzuki 1000 fuel injected bike that is notoriously lean from the factory. (lots of dead spots, and stumbles in the mid plus a nuedered top end) Instead of buying an expensive fuel programmer I went to radioshack and bought a 2$ potentiometer and wired it in place of the air temp sensor .by setting the pot to 10kohms it mimics 20 degree(f) air tempature and turned the bike into a smooth running monster. when it reaches above 80 I turn the pot back to 4.5k ohms to mimic 50 degree air.

    Now I'm going to do the same thing with my f75. I'm already running to big of a prop. the boat is a 2008 17 foot triumph skiff. it's 8' wide heavy and flat. with the 3 blade 13x15 it ran 37 at 5300. I wrecked that prop and got a smoking deal on a 13x17 four blade and the boat hits 35 at 5000. I like the handling much better. the boat needs more power so I am going to yank the plate and Bypass the intake air temp sensor with a homemade fuel controller. does' any body know the resistance values temp/ohms of the Yamaha's Iat?

  • #2
    What F75 are you talking about?

    The carburetor model has a restrictor plate in the intake. The fuel injection model does not.

    The fuel injection model has an intake air temperature sensor. The carburetor model does not.

    There is a bit more to making HP than just air and gasoline.

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    • #3
      fuel injected 07 model

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      • #4
        Originally posted by boscoe99 View Post
        What F75 are you talking about?

        The carburetor model has a restrictor plate in the intake. The fuel injection model does not.

        The fuel injection model has an intake air temperature sensor. The carburetor model does not.

        There is a bit more to making HP than just air and gasoline.
        from other threads you seem quite knoweldgeable on the subject of yammi ecu's. If I trick the thing into thinking it's colder than it is will it compensate with more fuel? without a restrictor to remove it seems like more fuel would be a moot point

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        • #5
          Originally posted by skidooguymxz View Post
          from other threads you seem quite knoweldgeable on the subject of yammi ecu's. If I trick the thing into thinking it's colder than it is will it compensate with more fuel? without a restrictor to remove it seems like more fuel would be a moot point
          Yamaha EFI's seem to run on the rich side IMO. Adding more fuel only should not offer any more power. Might be less. If you were to take away fuel you might get more power but at the expense of long term engine health.

          Now if you were to find a used serviceable F90 ECU, and you have determined that the only difference between an F75 EFI model and an F90 EFI model is the ECU, that would be one way to up the HP output.

          6D8-8591A-11-00. Yamaha ECM. F90TLR | eBay

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          • #6
            the airboxes are a different part number between the 90 and 75. a small aluminum collar necks down the intake right at the start of the airbox. I verified it in my 2007 f-75. pictures of the 75 include this part, pictures of the 90 do not. the 90's air box is ten dollars cheaper as well.... not saying it has anything to do with power but it is there

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            • #7
              I am not seeing it. According to the parts book the intake manifold is the same part number for both models. What am I missing?

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              • #8
                f75 air intake
                6D6-14440-00-00 YAMAHA SILENCER ASSY, INTAK

                f90 intake
                6D8-14440-01-00 YAMAHA SILENCER ASSY, INTAK
                the f90 is ten dollars cheaper and a different number

                your parts are from the tiller models not that should change anything.

                the diagrams don't show the view of the air box to see the piece but google image searches of the actual part do and it is 100% in mine. I can't 100% say the same thing ain't there in a 90 though

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                • #9
                  Well be sure to let us know the results of your experiment.Interesting to say the least...

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                  • #10
                    Originally posted by skidooguymxz View Post
                    f75 air intake
                    6D6-14440-00-00 YAMAHA SILENCER ASSY, INTAK

                    f90 intake
                    6D8-14440-01-00 YAMAHA SILENCER ASSY, INTAK
                    the f90 is ten dollars cheaper and a different number

                    your parts are from the tiller models not that should change anything.

                    the diagrams don't show the view of the air box to see the piece but google image searches of the actual part do and it is 100% in mine. I can't 100% say the same thing ain't there in a 90 though
                    Interesting.

                    By the way, if you look at the diagrams I posted they both are for TLR models. The R denotes remote control. The T is for trim and tilt.

                    As pana sez, keep us posted. Be careful throttling up for the first time after the motor has been modified. Don't let all that extra power get away from you.

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                    • #11
                      Originally posted by boscoe99 View Post
                      Interesting.

                      By the way, if you look at the diagrams I posted they both are for TLR models. The R denotes remote control. The T is for trim and tilt.

                      As pana sez, keep us posted. Be careful throttling up for the first time after the motor has been modified. Don't let all that extra power get away from you.
                      just compared the tlr models and got the same 1 digit part number difference and the ten dollar price difference.

                      sarcasam aside the piece is there in the efi f75 weather you believe it or not. maybe the same piece is in the 90's box, maybe not. I can't speak from experience.

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                      • #12
                        No sarcasm intended. I don't know what specific illustrations you are looking at.

                        The two parts catalog images that I have posted above, one from a 2007 F75TLR and the other from a 2007 F90TLR, clearly indicate the same part number intake manifold is used. Both have the 6D8 prefix.

                        I don't disagree with you that other models use a 6D6 prefix intake manifold.

                        You said you had a 2007 F75TLR. I tried to compare it with a like year model F90TLR.

                        I note that the 6D6 prefix intake manifold is also used on both F75 and F90 models. I have no idea what Yamaha was thinking or why they did/do what they did/do.

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                        • #13
                          Now that I inspect it some more, I think the confusion lies with the boats.net parts catalogs. They appear to be lumping different F75 and F90 models together. The Yamaha parts catalog at Yamaha Outboards allows them to be seen by production year. One can get a better understanding of exactly what parts are used on a specific serial number motor.

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                          • #14
                            we are talking differnet parts. I'm talking about the air box not the manifold. look under intake 2. just verfied on the yamaha site they are different

                            14 6D8-14440-01-00 SILENCER ASSY, INTAKE f90

                            14 6D6-14440-00-00 SILENCER ASSY, INTAKE f75

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                            • #15
                              I see said the blind man. My bad. I was suffering target fixaton on the wrong target.

                              If it is suspected that the F75 air box has a restriction wthin it run the motor with the box removed and see what happens.
                              Last edited by boscoe99; 07-13-2017, 12:50 PM.

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