23' Seaway Inboard to Outboard Project

Discussion in 'Downeast Projects and Boat Building' started by Waveland, Jul 17, 2019.

  1. Waveland

    Waveland Member

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    Hey everyone. Been browsing here for awhile, first time posting.

    I've got a 1978 Seaway 23 straight inboard that I have owned for a few years. It's been passed around a few times over it's life and it shows. Most recently I cut the wheelhouse off of the boat. It was homemade and very rough, and was starting to rot. The boat originally had a cuddy on which the wheelhouse was built.

    The boat has an old Nissan SD-33 diesel in it, and when I bought it there was a very large home-built bare plywood engine box, which I rebuilt in glass over ply. This was obviously not the original engine, and due to the size of the engine and box, which can not get any smaller, you needed to be a contortionist to access the cabin.

    I have never had any use for a cabin on such a small boat, and I view it as taking up valuable deck/ fishing space, so I've decided to make the boat a center console, remove the old diesel with very poor power-to-weight, and replace it with an outboard and custom bracket. I hope to add pictures of the boat soon and during the project. I'm not looking to make this boat a "masterpiece" but simply a more useful-to-me fishing boat.

    Also, just inquiring with people who have experience with these boats and/or the process of making the conversion. My main concerns are if the transom is robust enough to have an engine hanging off the stern, and weight distribution, as I believe this hull is relatively light. Any tips/advice welcome, and I'm sure I'll be picking your brains more along the way.
     
  2. Waveland

    Waveland Member

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    Screen Shot 2019-07-17 at 2.03.58 PM.png Screen Shot 2019-07-17 at 2.03.33 PM.png Screen Shot 2019-07-17 at 2.03.05 PM.png Screen Shot 2019-07-17 at 2.02.34 PM.png
     
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  3. WoundUpMarine

    WoundUpMarine Captain

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    Definitely going to follow this. I have the same boat, 23 Seaway with a 55hp perkins in it. No house top, but a small forward cuddy. Make sure you beef up the transom wherever you add the bracket to, they definitely were not designed to take any weight or torque of an engine.
     
  4. Toolate

    Toolate Captain

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    Looking forward to it! What is the transom construction now?
     
  5. Waveland

    Waveland Member

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    The transom seems to be solid fiberglass, but as WoundUp stated, it definitely could use some beefing up. It seems pretty thin.

    I’ve got the cuddy cut down roughly flush to the gunnel, where I can start adding glass back to it to strengthen and shape etc.

    Weather went south today, but will add some more pics when I get a chance to take some.
     
  6. WoundUpMarine

    WoundUpMarine Captain

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    There's mine, solid fiberglass and very thing, you can push on the side of the boat and flex it. Adding an outboard will be a great project and it shouldn't take much hp to make the hull slide nicely. I'm hoping to have a 130hp volvo diesel that will go in mine in another year or two.
     

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  7. Waveland

    Waveland Member

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    Yup! Same boat. Keel is identical, and yeah the hull flexes a bit so I plan on adding in a few knees to stiffen her up a bit.

    A 130 should push her along nicely, and by nicely I mean right out of the water! I also had thought about going with a smaller but more potent diesel to keep the bulk of the weight in the middle of the boat, but the thought of possibly having to change the running gear etc. has turned me off to the idea.
     
  8. Toolate

    Toolate Captain

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    I’m no expert but think you would want to laminate like 3 layers of coosa or plywood to that transom plus the knees and tie them into the stringers. Again no expert.
     
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  9. Waveland

    Waveland Member

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    Thanks for your input, I wasn’t sure how much I’d need to add, but that sounds like a good start. I’m not very savvy with glass. I weld, and plan on fabbing the bracket etc. myself, but wood and glass are not my cup of tea. I’m handy, but not a boat builder.
     
  10. Eastporter

    Eastporter Captain

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    Do a search for Seaway bracket and Flowers Boatworks put an outboard on a Seaway a few years ago= put an extra layer of plywood/coosa and knees for support.
     
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  11. willbfishin

    willbfishin Senior Member

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    We are in the process of finishing a 26 footer that’s getting a 200hp Yamaha . The transom is 1/2 inch of solid glass then 3 layers of 3/4 inch marine ply with glass between each layer then another 3 layers of glass , plus 2 knees that are glassed to boat bottom and run up 3/4 of the way up transom .
     
  12. Eastporter

    Eastporter Captain

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  13. jdickau484

    jdickau484 Senior Member

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    Which hull you got going?
     
  14. dnauhei

    dnauhei Senior Member

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    Hey, my boat has a SD33! What are you doing with the engine? I might be interested in the transmission.
     
  15. Cool Boat

    Cool Boat Member

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    The last time I had a question regarding Coosa and transoms I spoke with Tom, a tech, at Coosa. 877-249-1010 They cannot engineer the design for you but can provide examples of what is being used in shops. Good luck with it. We thought about this same option with the 23' hull we are refinishing but didn't want to put a whole bunch of $ into an outboard that may not work out on the very narrow round bilge hull we have. We rebuilt a DD453 to put in the boat, and if we don't like it, will find a donor truck chassis and have some fun with it. Looking forward to seeing your pictures. Good luck.
     
  16. Quik Fix 16

    Quik Fix 16 Senior Member

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    I have done a few inboard to OB conversions and this is what I have done. I use 3/4" plywood and make sure the transom is tied to the stringers. You weld so making strong knees is simple for you. Please post pictures as you go.
     

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