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Jim Smith 100' Sportfish backing down... a street?

Discussion in 'General Sportfish Discussion' started by YachtForums, Nov 26, 2020.

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  1. mapism, Nov 28, 2020
    #21
    mapism

    mapism Senior Member

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    Ok, if you say that the one in Patsea ain't an u/w exhaust, then we are on the same page:
    - port along the hull bottom = underwater exhaust.
    - port on the stern = non-u/w exhaust, requiring some kind of silencer.
    And that's regardless of the exact position of either solution.

    Now, I still can't see why midship u/w exhausts should not work well with SF boats, when it's widely used also in much faster boats, like Magnum and the likes.
    In fact, the water flow along the hull bottom tends to push the aerated area not only backwards, but also towards the external hull sides, so there's zero chance of interference with props, with the only possible exception of hard steering at speed, whose relevance is marginal at best.

    But hey, I guess that neither Jim Smith nor any other SF builder are interested in my opinion on that! :)
  2. Capt J, Nov 28, 2020
    #22
    Capt J

    Capt J Senior Member

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    Trolling is the reason why. The underwater exhaust makes the wake behind the stern full of bubbles and not clean. This interrupts how the fish can see the lures. You want a clean wake outside of the prop wash for the lures. Tribute built the last "Speed Merchant" sportfish for Dick Moroso (racing). It was 60' and almost hit 50 knots with a tuna tower and only a pair of C18 cats. Tribute put steps in the hull to get that speed, but the wash at trolling speed was horrible because of all of the bubbles that the steps introduced. Most all (not all) sportfish use a traditional exhaust on the transom like seen in the photo's. A few do some sort of underwater exhaust but it's rare.
  3. mapism, Nov 29, 2020
    #23
    mapism

    mapism Senior Member

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    Thanks for the explanation, makes good sense.
  4. Capt J, Nov 29, 2020
    #24
    Capt J

    Capt J Senior Member

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    If not for that, it would be VERY interesting to see what speed one of these boats would do with Arnesons or jets set up to take advantage of the hull and maximum speed. All of these big SF are knocking on 50 knots door step with traditional shafts and generally 16v2000's. The cold molded sportfish are about 1/3 lighter than their production brothers and ride much better too.
  5. Slimshady, Nov 29, 2020
    #25
    Slimshady

    Slimshady Senior Member

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    Spencer has a 64 jet almost ready, should be exciting to see.
  6. Capt J, Nov 29, 2020
    #26
    Capt J

    Capt J Senior Member

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    They did a 50' express for a an owner that I know that turned out well. Will be interesting to see the speeds on the 64' will be.
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