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15hp strange loss of power

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  • #31
    Upps. got my Crank position sensor mixed up with the TPS. Need to keep brain in gear.
    RIPSAWSBOAT 1998 Yamaha 25HP Model 25N 4/97 25MSHW

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    • #32
      Originally posted by grf00 View Post
      Upps. got my Crank position sensor mixed up with the TPS. Need to keep brain in gear.
      A slip into neutral is good once in awhile!!!
      Scott
      1997 Angler 204, Center Console powered by a 2006 Yamaha F150TXR

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      • #33
        So i'm going to start again today, have a look at the carb - new fuel. timing is spot on and the sync is fixed so no adjustment
        here is a parts catalogue

        http://www.twineye2002.com/products/...rts%20Book.pdf
        sorry cant find it in English

        so loads of power till I hit half power then it just does not want to go any further/faster. would be as if the timing had not advanced if that makes sense
        Last edited by Gmcken34; 07-03-2014, 07:13 AM.

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        • #34
          Originally posted by Gmcken34 View Post
          So i'm going to start again today, have a look at the carb - new fuel. timing is spot on and the sync is fixed so no adjustment
          here is a parts catalogue

          http://www.twineye2002.com/products/...rts%20Book.pdf
          sorry cant find it in English

          so loads of power till I hit half power then it just does not want to go any further/faster. would be as if the timing had not advanced if that makes sense
          Downloaded that PDF attachment but it won't open for some reason.

          Re the carb. If your pulling it apart again, from your description, find the main jet and make sure that's spotless and the orifice it screws into is clean..


          Good luck
          Scott
          1997 Angler 204, Center Console powered by a 2006 Yamaha F150TXR

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          • #35
            It opens now.
            RIPSAWSBOAT 1998 Yamaha 25HP Model 25N 4/97 25MSHW

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            • #36
              Originally posted by grf00 View Post
              It opens now.
              Still won't open on my lap top for some reason.

              I'd rather have a parts fisch anyway, much easier to find the appropriate jets and refer back to them...
              Scott
              1997 Angler 204, Center Console powered by a 2006 Yamaha F150TXR

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              • #37
                Hi all,

                Got a barrel of water so I can now test on the drive, carb is spotless so not a carb issue?
                Checked fuel line for air ingress(nothing)
                have used a spare coil and still the same issue
                running the engine in a big barrel of water I can engage gear but still wont go over about 1/2 power
                out off gear it can rev up no issue(no misfire and not sluggish)
                all I can think of now is again the CDI(faulty above 1/2 power/when quicker spark is required)

                So now my question is - is this possible can a CDI unit fail in such a way or do I have a deeper Issue?

                Thank you

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                • #38
                  What you are asking is above me. Probably like a solid state voltage regulator, pretty hard to check without special stuff. However after looking at your motor, I do not see a throttle position sensor. Appears to me motor is totally mechanical advance. Sure looks like an advance lever on top of motor with a link back to carb link. However, as long as someone has not messed with it, it should be OK. However I may be missing something. Do you have prop off? Not sure how you are running it in a barrel WOT and keeping water in barrel. I can test mine since I live on the water but tied up, it throws water ever where. Even more interesting, sitting still tied up, the idle in gear is different then the idle running down the creek. Anyway, if you have the prop on and can keep it with water, try (CAREFULLY) with it at WOT in GEAR and with a little mister, hit it with some 50-1 fuel mix. (just a little) If it bogs, then it was getting fuel. If it revs up, you still have a fuel problem or a advance problem. (do you see the TPS on the carb?) find it interesting you have warm water going to carb..I assume for emissions
                  Last edited by grf00; 07-05-2014, 06:11 PM.
                  RIPSAWSBOAT 1998 Yamaha 25HP Model 25N 4/97 25MSHW

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                  • #39
                    Originally posted by Gmcken34 View Post
                    running the engine in a big barrel of water I can engage gear but still wont go over about 1/2 power
                    +1 on the above post.

                    If your prop is on, while in the tank, IN GEAR, it won't rev up to WOT. The prop is grabbing too much water. In neutral, theirs NO drag on the engine and will rev fully..

                    Kinda like trying to go wide open in youer car while holding the brakes half on...

                    Even tied to a dock, you'll get better results but not the same as un- teathered, let that engine rev, under normal load and see how it performs..
                    Scott
                    1997 Angler 204, Center Console powered by a 2006 Yamaha F150TXR

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