I/O to outboard

Discussion in 'Boat Design' started by Rranger, Nov 26, 2020.

  1. ondarvr
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    ondarvr Senior Member

    125 hp is considered low hp.

    A splash well adds an extreme amount of stiffening and strength.

    Adding a bracket, or mounting an outboard to the transom without a splash well, normally requires knees or other methods of additional support.
     
    Last edited: Dec 16, 2020
  2. Rranger
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    Rranger Junior Member


    Again thank you, and the splashwell design as I have figured out will definitely add a lot of strength.
     
  3. Rranger
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    Rranger Junior Member

    F1F46CFA-10A5-4360-8CA4-60FF4077033A.jpeg
    Got my 3/4” plywood both installed. Covered with two pieces of 1708. 3” and 6” side and bottom overlap. Could run a piece of 9” overlap around the sides and bottom if needed? Or do I need one more sheet of mat with 9” overlap? I’m thinking I will put the 9” overlap piece both sides around the outside edge. Mat is 2 hours away and would be waiting til Tuesday to get it. Then I can start looking at cutting the transom to the width and depth for the engine. I got a article somewhere points out I believe 36” wide hole at the back where the motor hangs, which seems excessive. I’d like to keep as much wood above the engine mount angled up and towards the new sides of the splashwell, to keep as much backsplash out as possible. And a depth forward to 24” to accommodate tilting the motor forward when I build the splash well. Any rule of thumb out there?
     
  4. ondarvr
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    ondarvr Senior Member

    The dimensions are motor specific, but production boats typically have extra room to allow for the greatest dimensions that may be required.

    You can make the transom cutout and motor well any size that allows your motor full movement.

    I go as small as possible on both. Just remember if you plan to repower in the future the required dimensions may be different.
     
  5. Rranger
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    Rranger Junior Member

    ondarvr said:
    The dimensions are motor specific, but production boats typically have extra room to allow for the greatest dimensions that may be required.

    You can make the transom cutout and motor well any size that allows your motor full movement.

    I go as small as possible on both. Just remember if you plan to repower in the future the required dimensions may be different.



    I will be measuring twice . I see your in the resin, gelcoat business, on another subject I have a 1 gallon two part gelcoat mix I’ve had for probably three four years, any chance it would still be good, never been opened.
     
  6. ondarvr
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    ondarvr Senior Member

    The shelf life is normally 3 months.

    There is a small chance that it's still liquid, if it is, it will probably cure very slowly.

    If it does get hard there's not a good chance it will cure completely.

    So only use it someplace that may not be important.
     
  7. Rranger
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    Rranger Junior Member




    Sounds like a punt to the dump can. Thanks.
     
  8. Rranger
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    Rranger Junior Member

    5B3063FE-116F-420C-B049-13EB8E4BEBF2.jpeg Cut off 18” of the old top of transom to see what I’m up against to tie in my motorwell. From what I’ve gathered recommended opening on the transom for the engine is 33” wide. If I go off my outside stringers I’d be 30” and be able to use all one piece on each side to tie the stringer, transom, and motorwell all together. So that’s the plan. Couple more under the floor braces connecting to the two inside stringers and it should be solid.
     
  9. Rranger
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    Rranger Junior Member

    Bit of a hiatus while I decide whether to stick with my 20” shaft 125hp or continue to look around for something up to 175hp with a 25” shaft. I’d far rather have the 25” shaft. Not a lot out there so will put er on hold til after New Years.
     
  10. ondarvr
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    ondarvr Senior Member

  11. Mr Efficiency
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    Mr Efficiency Senior Member

    You can get extensions, but some outboard mechanics are leery.
     
  12. Rranger
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    Rranger Junior Member

    Yes I have bought one in the past from Bay Manufacturing. $750- $800 later you have a extension. The little 5” extension for the drive shaft in particular didn’t impress me much and to Mr. Efficiency's point I could see why mechanics might have had concerns.. The slightest bit of slack in the fit of the extension on the driveshaft could lead to some engine issues. Another just as important reason besides the shaft length for maybe repowering, is to get some more hp. I’d like to get 15-175 hp.
     
  13. ondarvr
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    ondarvr Senior Member

    They are common in this area, no real problems reported.

    The fit and connection is the same as whats on both ends of the existing drive shaft.
     
  14. Rranger
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    Rranger Junior Member

    Dealing on a 2000 carbureted Johnson Ocean Pro 150 hp with the extra long shaft. Was never going to be happy with the 20” shaft so hopefully this pans out on the 27th. . Then I can get hacking on the transom down to the right height and then put my bracing in and then complete the splashwell and fiberglass it all up. And then gelcoat the back of the transom and all the disturbed area in the back of the boat. The old Johnson will fit the theme of the old gangster sangster.
     

  15. Rranger
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    Rranger Junior Member

    90B3ECA6-E85B-4207-9A68-FF6F139C3E55.jpeg 39232098-FB8B-4EE7-8520-E73FE4D235E6.jpeg Bought the Xl shaft Johnson, should be here tomorrow or it will be day after New Years. Got knee braces and sides of motorwell roughed out. Left some extra material til I get the exact measurement of the shaft length for the Johnson then I can start hacking the transom and adjust bracing accordingly.
     
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