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Separating the upper gear housing and transom mount on a Yamaha stern drive

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  • Separating the upper gear housing and transom mount on a Yamaha stern drive

    I have a 1995 Cobia with a Yamaha stern drive. I am having trouble with the shifter sequencing with the carburetor. I have found that there is a common problem with the shifter located in the upper gear housing. I have removed what appears to be all of the bolts from the studs attached to the transom mount, but I cannot get the upper gear housing to even start to separate from the transom mount on the starboard side. I can only find three nuts attached to studs from the transom mount on either side of the upper gear housing. Does anyone know of additional fasteners that may be holding me up, or is it possible that the upper gear housing is seized onto the stud(s)? I can get some very small separation on the port side.

  • #2
    Re: Separating the upper gear housing and transom mount on a Yamaha stern drive

    6 nuts, 3 each side, plus the trim rams. Once these are removed it is normally a simple matter of brute force, carefully applied.
    There are suggestions elsewhere about placing a 4x4 timber across the transom then letting the leg drop onto it. This should break away any corrosion without damaging the transom mount or the leg studs.
    That said, i cannot say if this works because I've been able to get my leg off with a simple pull.
    Once off, make sure you grease the mounting studs before putting the leg back on.

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    • #3
      Re: Separating the upper gear housing and transom mount on a Yamaha stern drive

      Originally posted by triman View Post
      6 nuts, 3 each side, plus the trim rams. Once these are removed it is normally a simple matter of brute force, carefully applied.
      There are suggestions elsewhere about placing a 4x4 timber across the transom then letting the leg drop onto it. This should break away any corrosion without damaging the transom mount or the leg studs.
      That said, i cannot say if this works because I've been able to get my leg off with a simple pull.
      Once off, make sure you grease the mounting studs before putting the leg back on.
      Thanks for your response. I found some corrosion around a couple of the studs, so I used a 50/50 mixture of transmission fluid and acetone as a penetrating oil and continuously added this to the studs. I just learned about this trick and used it on some rusted tools I have in the garage and it worked awesome. After a few days, I could see that most of the corrosion had dissipated and I was able to get the port side to separate a bit more. I slowly inserted wedges into the port side as I struck the starboard side with my 48 oz dead blow mallet trying to loosen up the corrosion. This seemed to work as the wedges became easier to drive into the port side. Eventually, the two housings started to separate at the bottom of the starboard side and I was able to get the a screwdriver in and begin to pry the upper gear housing away. As I got the housing separated, I did find that there was corrosion on a few of the studs and that the studs were not perfectly aligned in the upper gear housing. These two factors appear to be what kept me from easily separating the two housings. Gonna use a lot of lubricant on these studs going back together to help keep this from happening again. Now, if I can just figure out how to fix the problem that required me to separate these two housings. I think it might be helpful to others to know that I found tire spoons worked great as wedges and prying tools between the two housings. Worked better than any of the Snap On tools I normally so proudly prefer to use.

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      • #4
        Re: Separating the upper gear housing and transom mount on a Yamaha stern drive

        I forgot to mention earlier that, unlike the Mercruiser legs, the Yamaha should be in neutral when taking the leg off the transom.
        Good to hear you got the thing off - hopefully without distorting the monuting surfaces.

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        • #5
          Re: Separating the upper gear housing and transom mount on a Yamaha stern drive

          If you dont have a Clymer manual yet for the Yamaha Sterndrive, I would suggest you get one. They are available on ebay. I found it invaluable when I did mine. It is a fairly involved job, and you will need to know the specs to put it back together.

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          • #6
            Re: Separating the upper gear housing and transom mount on a Yamaha stern drive

            Originally posted by triman View Post
            I forgot to mention earlier that, unlike the Mercruiser legs, the Yamaha should be in neutral when taking the leg off the transom.
            Good to hear you got the thing off - hopefully without distorting the monuting surfaces.

            Yeah, I did know to put it in neutral. It doesn't look like I did any damage to the housings either. I have been around the block a few times and was watching from the very beginning to see if I was creating any damage. It looks like everything came off clean. Now I just have to wait for the parts to come in that I had to order to put it back together again.

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            • #7
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              Re: Separating the upper gear housing and transom mount on a Yamaha stern drive

              Originally posted by ricovw View Post
              If you dont have a Clymer manual yet for the Yamaha Sterndrive, I would suggest you get one. They are available on ebay. I found it invaluable when I did mine. It is a fairly involved job, and you will need to know the specs to put it back together.

              Thanks, that is one of the first things I did before I tried to dig into the thing. I have never had a boat before and am learning a bit about them. The Clymers manual helped out a bit, but is not real detailed, so it left me wondering if I had missed something. I know that typically the cases should separate pretty easily, but mine was being stubborn.

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