Curved Transom and Twin Engines

Discussion in 'Powerboats' started by 96720, Apr 21, 2011.

  1. 96720
    Joined: Apr 2011
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    96720 Junior Member

    I’m beginning a rebuild of a 1961 Glasspar Avalon. Will the curved transom design be suitable for twin outboard engines? I’ve always heard people say that curved transoms needed to be “shimmed” before twin engines could be installed. So, what would the recommendation be on redoing the transom? Leave it curved? Rebuild with the curve then shim it flat? Or, make it flat during the rebuild? Any ideas or suggestions will greatly be appreciated. Thanks.
     
  2. tom28571
    Joined: Dec 2001
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    Location: Oriental, NC

    tom28571 Senior Member

    Whichever is the simpler and easier would be my take on it. Nothing wrong with just shimming unless the curve is too great for it to be practical. A curved transom often need shimming or wedging for even one outboard.
     
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  3. 96720
    Joined: Apr 2011
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    96720 Junior Member

    Thanks for the quick reply, Tom. So should I cut the outer skin about 2/3rds to ¾ ths of the way down to the bottom of the hull and make the plywood rebuild create a flat transom line for the motor mount?
     
  4. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    The first thing you need to do, before cutting anything is to see how much engine swing you'll lose if you just mount them, without shims. A mildly curved transom may not need any shims at all. On a more rounded transom you can shim the outboard side of the engine bracket, until it all but bottoms the inboard side out. Either of these techniques is usually more then enough for the average curved transom. Only if you can't get enough steering swing using one or the other should you consider hacking away at the transom. Just gluing a hunk of plywood to your transom to straighten it isn't going to transfer the torque from the engine bracket to the boat bottom (what a healthy transom does). A transom with a flattened "jog" in it will need to be heftier then a straight or curved one, so consider you options wisely.
     
  5. tom28571
    Joined: Dec 2001
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    tom28571 Senior Member

    As Paul said and I did not make clear enough, don't cut into the existing transom.
     

  6. 96720
    Joined: Apr 2011
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    Location: big island of hawaii

    96720 Junior Member

    thanks

    Thanks for the advice Paul and Tom. I won't cut the transom and will replace the original contour. The original transom looks like it can accomadate twins without problem but, I'll check and see after the rebuild.
     
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