converting i/o to outboard

Discussion in 'Powerboats' started by captainstogie, Jul 30, 2004.

  1. captainstogie
    Joined: Jul 2004
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    Location: Corpus Christi, TX

    captainstogie Junior Member

    I am considering converting my i/o to an outboard.
    Boat: 1990 Rinker 28 ft Fiesta Vee 250
    Engine: 5.7 Liter V8 Mercruiser 230 hp

    I have found a boatyard that will pull it re glass the hole in the transom, which is below the waterline. He showed me another boat he is doing this with and it looks very well done. There is another shop that will pull the engine for me relatively cheaply. So now I will have a solid boat with no power. What is the process for mounting o/b. I had originally thought about going with twin counter rotating screws, but that may be too much money for this boat. How big of a single o/b can I mount, what does it take to mount it, and what are the potential problems I am likely to incur?

    Reason for doing this is the boat must stay in the water and the maintanence on it is a killer. It is located in the Laguna Madre area of the Texas coast which boasts the highest salinity rate second only to the Dead Sea!

    Any info would be greatly appreciated. Also any names of manufacturers of brackets and the like I am likely to find useful.
  2. dereksireci
    Joined: Jun 2004
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    Location: South Carolina

    dereksireci Senior Member

    Bracket Mounted Outboard

    The first issue to consider is how much radius does the transom have? A lot of radius does not lend itself well to certain types of outboard engine brackets. I would look at an Armstrong or Stainless outboard bracket. Salt Shaker used to make a fiberglass bracket but I don't know if they're still available. If you can't afford twins then I think 250 hp for a 28' boat unless it's real light. I used to run a 26' Edgewater and the Yamaha 250 two stroke pushed it pretty well, but sometimes we wished we had twins.

    Since your transom wasn't designed for all that weight to be hanging back there you may need to beef it up some. Before you fix the outdrive hole, measure the thickness of the transom and note what kind of core is in there. Ask the bracket manufacturer for advice on this as well as installation height.
  3. Corpus Skipper
    Joined: Oct 2003
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    Corpus Skipper Hopeless Boataholic

    Howdy captainstogie! I'd tend to agree with dereksireci, an Armstrong bracket would be the way to fly. They'll work with just about any transom configuration. Your I/O was 230 hp, so 225-235 hp outboard should fit the bill. Make it a 4 stroke and it should be nearly as efficient as your old I/O if not more so with EFI. What do you intend to do with the "hole" left over from the old engine? I assume you want outboard so you can tilt the motor out of the water. Be aware that the motor may not clear the water completely if bracket mounted due to the weight being further aft and causing the stern to settle a bit. Are you at Tropic Isles, Padre Isles, or a marina? Maybe a lift would be a better solution.
  4. yipster
    Joined: Oct 2002
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    yipster designer

    longtitudal centre of gravity will come backward so move some weight forward.
  5. captainstogie
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    captainstogie Junior Member

    Thanks for the info. I appreciate it.
  6. captainstogie
    Joined: Jul 2004
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    captainstogie Junior Member

    I'm getting a lot of very good advice. Glad I found this site. Thank you.
  7. captainstogie
    Joined: Jul 2004
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    Location: Corpus Christi, TX

    captainstogie Junior Member

    Thank you for the help
  8. Mick
    Joined: Aug 2004
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    Location: Minnesota

    Mick New Member


    Being a dreamer and not a boat designer and given my lack of experience with such things, for better or worse I am left to my imagination. I'd like to ask a couple of questions which may help lead to another alternative solution.

    Since it will be necessary to rebuild or reinforce the transom, why not make it a notched transom with a splashwell?

    If feasible, this would:
    1. Eliminate the cost of adding a motor bracket.
    2. Lessen the aftward movement of the longitudinal center of gravity.
    3. The careful positioning of the motor height-wise might help ensure the motor is out of the water when fully tilted up.

    Does this sound like a reasonable approach?

    This is my first post. I have been looking in for a while now and enjoy the knowledge and demeaner of the site. You've got a wonderful site going here!


  9. articman
    Joined: May 2004
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    Location: Nunavut Canada

    articman New Member

    I converted my 24 foot sea ray to a outboards. saved about 300 lbs in weight. installed twin 90's and bought my self some worry free off shore travel.

    Used a D&D marine bracket, cost was less and after seeing an Armstrong Bracket the D&D has a full back in it.

    Yes it changed the handeling of my boat, trim tabs took care of most of the problems, but getting the set up was the hardest part. Do not let your outboar dealer tell you what the setting above the bottom is, stay with what the supplier tells you.

    I went with 25 inch legs mounted 2 1/2 above the bottom, dealer said no, but after lots of trail and error we went back to the recommended set up and it work good.

    This week we plan100 mile off shore trip, will let you know aht we find .
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