Conversion to Merc

Discussion in 'Gas Engines' started by williampagano, Nov 14, 2012.

  1. williampagano
    Joined: Nov 2012
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    williampagano Capt Bill

    I would like to convert to a mercruiser from an OMC Stringer. Beside the transom and stringer work necessary, what are thoughts on Alpha I, Gen 2, or Bravo upgrades. The boat is a 1970 Formula 233 in good shape.
     
  2. gonzo
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    gonzo Senior Member

    The Alpha Gen 2 is the best option for performance. The Bravo is a stronger drive, but also creates more drag. Unless you have a hotrodded big block the smaller drive should do fine.
     
  3. marshmat
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    marshmat Senior Member

    For a 5.7L or bigger motor, I'd pick the Bravo 1 or Bravo 3. I have seen 5.7s with Alphas but that's getting to be a bit of a stretch for a small, cheap drive intended for 20' bowriders. Reliability may suffer in the long term.

    A 5.0L or smaller will be quite happy with the Alpha unless you've done something crazy like putting 15 psi of supercharger on it.
     
  4. williampagano
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    williampagano Capt Bill

    Thanks for your info. The present OMC 210 is a little under powered with four or more aboard. Will the Alpha Gen II give better power? Or do I need to upgrade the original Chevy engine?
     
  5. gonzo
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    gonzo Senior Member

  6. FMS
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    FMS Senior Member

    It would be a good time to consider swapping the engine as well; the drive alone will probably not deliver the noticeable performance improvement you seek although it will be advantageous overall. What is your boat's current speed at WOT?
     
  7. CDK
    Joined: Aug 2007
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    CDK retired engineer

    There is a wealth of information on that website.
    But bear in mind that they are talking about Mercuiser horses where they mention "hp". The most important load limit for any drive is torque, but that info is missing.

    An engine delivering 300 hp (DIN) at a substantially lower rpm than a Merc will destroy the Alpha One in seconds!
     
  8. Submarine Tom

    Submarine Tom Previous Member

    You'll be a lot happier with the Merc than that OMC!
     
  9. Frosty

    Frosty Previous Member

  10. FMS
    Joined: Jul 2011
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    FMS Senior Member

    A Yanmar diesel cannot be coupled to an alpha drive. The diesel's torque will destroy an alpha drive.
    A yanmar engine and bravo x installed will cost 2-3 times the formula 233's bluebook.
     
  11. Frosty

    Frosty Previous Member

    Where does it say that --in a book.

    I put a merc 225 on a boat. On the transom was a plaque that said max HP 80.

    You will have to be bit careful with the throttles then......

    Pssst,--- the yanmar 6LP range is Toyota land cruiser 1HD engine. But dont tell anyone.

    The Yanmar will run 1000s of hours where as the American iron push rod engine with its cracking manifolds will be 3 seasons if your lucky.
     
  12. FMS
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    FMS Senior Member

    Consult a marine mechanic and ask Mercruiser. An alpha drive coupled to a Yanmar 6LP diesel won't last on a Formula 233.

    An inexpensive chevy block will last 1,000 hours and an inexpensive alpha drive will last about the same in salt water. Invest what is reasonable for the use the boat will get. There is nothing wrong with a yanmar bravo x installation provided you want to spend the money on a stronger better made drive.
     
  13. williampagano
    Joined: Nov 2012
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    williampagano Capt Bill

    Thank you for all your comments. Obviously cost IS an issue. I would like to reuse the existing OMC engine and mate it to an Alpha II. Is this realistic? After redoing the transom and possibly the stringers, I will be in for the book value already.

    Where can I get guidance on what to use and how to use it?? I note there are different gear ratios for the outdrive. How do i make a selection?
     
  14. Willallison
    Joined: Oct 2001
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    Willallison Senior Member

    Personally, I'd turf all of it and put an outboard or two on the back....
    We have an Oz-built copy of the 233 with a pair of 225hp Optimax's. Wouldn't even dream of swapping them for sterndrives....

    I know... cost is an issue... but just thought I'd throw it into the mix....
     

  15. gonzo
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    gonzo Senior Member

    I just changed a pair of 454s from charter boat. They had over 5000 hours and were still running. The owner wanted new engines to make sure they wouldn't need service in the middle of the season.
     
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