Yamaha sterndrive to Mercruiser sterndrive Information

Discussion in 'Sterndrives' started by Morris Wallace, Aug 29, 2017.

  1. Morris Wallace
    Joined: Aug 2017
    Posts: 2
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    Location: Maryland

    Morris Wallace New Member

    I need to replace my Yamaha sterndrive for the lack of Yamaha discontinuing it's outdrive industry. I'd like to replace the drive set-up with a Mercruiser Alpha I or II. Has anyone ever performed such a trans-version. It currently has a GM 454cu in engine. I have gathered some parts from a 454 previous boat such as; Mercruiser risers, bell housing and flywheel spine for mercruiser with exhaust. My concern is the mounting shape of transom differences between the Yamaha Plate and the Mercruiser Plate. Any help and advice would be appreciated.
     
  2. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    Are you sure there is much difference between a Yam and an Alpha I?
     
  3. Morris Wallace
    Joined: Aug 2017
    Posts: 2
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    Location: Maryland

    Morris Wallace New Member

    Hello CDK, this is my main question. I'm not sure if it's a direct removal and replace. I'm going to find a Mercruiser thru-hull transom gasket
    and match it with the extra Yamaha transom plate I have to see if there's any variables.
     
  4. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    Your drive is (I guess) from the era before the Alpha I. As far as I can remember, at the time the Merc and the Yam were identical except the paint color.
    I once replaced a pair of old Mercs with Alpha I and had to modify the transom holes just a little bit with a hacksaw.
     

  5. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    I don't think you'll want the Alpha, regardless of generation. You'll want the Bravo bolted up to the back of that MK4 Chevy. It's usually about power output and torque. How much is the 454 producing? There are some transom plate difference, but not much that can't be easily accommodated.
     
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