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2004 Yamaha 50hp 2-Stroke clutch/shaft Issue?

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  • 2004 Yamaha 50hp 2-Stroke clutch/shaft Issue?

    New to the forum here, a novice when it comes to boat motors. My issue: The boat will move forward at low throttle/rpm, but when I increase throttle to take off, the motor does several abrupt skips & revs way up until it looses bite completely. I have had 4 different props on the boat to test (all good props) and I do not believe it's a spun hub (no damage shown on any prop, marked them too to rule that out). Is there a clutch on these models in the lower unit? Keep reading about a clutch dog...? Almost sounds as if a gear or something is stripped. Or could it be lower unit completely? I would think if it was lower unit, it wouldn't go forward at all. I also do not think it is fuel related, like I said, boat will rev up fine, no sputters ever, go in reverse, & slowly forward is all. Any advice/opinions much appreciated!

  • #2
    usually when the clutch dog jumps out you can hear the grinding.

    spun hub you will not hear grinding

    that motors lower unit is spring loaded into forward, so if the sharp corners get rounded off and not able to hold onto the cutouts on the gear all it has to do is overcome the spring tension.

    time to take apart and have a look .

    might find metal on the drain plug magnet if this is just starting

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    • #3
      Can you check for adjustment in the gear shift mechanism and cable to ensure it's engaging forward.....have you dropped the lower unit lately, possibly getting the gear shift out of whack? Maybe drop the lower unit and manually put it in forward?

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      • #4
        Originally posted by robert graham View Post
        Can you check for adjustment in the gear shift mechanism and cable to ensure it's engaging forward.....have you dropped the lower unit lately, possibly getting the gear shift out of whack? Maybe drop the lower unit and manually put it in forward?
        as I said it is spring loaded into forward, so the linkage does not force it there.
        you have to force it into neutral and into reverse but not forward.

        but then if the linkage is not moving far enough to allowing it to go all the way into forward that could be a problem.

        I found that someone tried to force my brothers C60 into reverse some time and twisted the shift shaft and bent the pin in the prop shaft/clutch dog.
        which caused the dog and gears to make noise when put into neutral and adjusted properly.
        had the tear apart and replace parts to fix it

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        • #5
          I was just thinking that if the lower unit had recently been dropped for say a water pump replacement then maybe it got put back wrong or something....does this motor have a splined shift shaft going into the lower unit?

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          • #6
            Originally posted by robert graham View Post
            I was just thinking that if the lower unit had recently been dropped for say a water pump replacement then maybe it got put back wrong or something....does this motor have a splined shift shaft going into the lower unit?
            Appears to be splined but we don't know the exact model # : https://www.boats.net/catalog/yamaha...casing-drive-1
            Scott
            1997 Angler 204, Center Console powered by a 2006 Yamaha F150

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            • #7
              Where is this spring?

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              • #8
                inside the prop shaft
                https://www.boats.net/product/yamaha...bdb8f34d02c0a7
                Last edited by 99yam40; 1 week ago.

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                • #9
                  Lower unit has not been dropped lately, there have been a small amount of metal shavings on drain plug however. I have checked the shift cables, appears to be fully engaging into forward from what I can see with engine cover off. It's an '04 50TLRNC. 99yam40, in your first reply, are you speaking of the shaft that goes upward into motor could be stripped? or prop shaft, or both? Also, if I bought a whole new lower unit assembly, would a person who is mechanically inclined bolt up like plug & play? Perhaps the fix is in this link... Ouch!

                  https://www.boats.net/catalog/yamaha...casing-drive-1

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                  • #10
                    Or would finding the root cause be significantly cheaper to fix/take apart? Where I am, there is little to no one that I would trust to do such a job

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                    • #11
                      When you put the drive into gear, the prop will (should) spin easily in one direction and pretty much not at all in the other direction. Try that for both forward and reverse and see what happens. Even if you jiggle the prop back and forth, it should remain hard to spin. You may have to spin the prop a bit to help it get into gear, by the way.
                      2000 Yamaha OX66 250HP SX250TXRY 61AX103847T
                      1982 Grady Weekender/Offshore (removed stern drive & modded to be an OB)

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                      • #12
                        Originally posted by robert graham View Post
                        I was just thinking that if the lower unit had recently been dropped for say a water pump replacement then maybe it got put back wrong or something....does this motor have a splined shift shaft going into the lower unit?
                        The 2004 50 HP two strokes used a splined configuration that rotate a shift cam.

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                        • #13
                          Originally posted by Cornstar View Post
                          Lower unit has not been dropped lately, there have been a small amount of metal shavings on drain plug however. I have checked the shift cables, appears to be fully engaging into forward from what I can see with engine cover off. It's an '04 50TLRNC. 99yam40, in your first reply, are you speaking of the shaft that goes upward into motor could be stripped? or prop shaft, or both? Also, if I bought a whole new lower unit assembly, would a person who is mechanically inclined bolt up like plug & play? Perhaps the fix is in this link... Ouch!

                          https://www.boats.net/catalog/yamaha...casing-drive-1
                          Someone will need to tell me what the N in that model number(50TLRNC) means, I have no clue.

                          I would 1st put the controls into neutral, disconnect the shift cable at the motor, make sure both the control and the motor linkage sit in neutral detent, and them see if the shift cable fits back onto the motor linkage with out having to move either of them. Should just slide back on.

                          if out of adjustment, then adjust the cable end until it does fit properly.

                          If that does not help , then take the lower unit apart to see what is wrong and what it will take to fix it.

                          problem with that is without the proper tools it can be difficult to do.
                          I will look for the thread I started for my brothers C60 so you can look thru it and the one I did on my C40. those should be close enough to yours to get some idea.

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                          • #14
                            well I got locked out for awhile so here are the other threads I mentioned
                            http://www.yamahaoutboardparts.com/f...-while-idleing

                            and

                            http://www.yamahaoutboardparts.com/f...ls-replacement

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