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3 exhaust through hulls

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  • 3 exhaust through hulls

    Anyone have a pair of 3 exhaust through hills to match these:
    Click image for larger version

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    The only plastic through hulls I have are these 2 center exhaust from when it was repowered 4 cyl to v8:
    Click image for larger version

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  • #2
    OEM Glasply are 4" for V8's and when I added two additional exhaust thru hulls I found them on eBay. At the time I found many 3" available. I would suggest you add exhaust flappers though.
    "Joint Venture" 1978 28' twin 2017 Vortec roller cam 383/6.3L 350hp engines - You name it, I've either replaced it, restored it, rebuilt it or repaired it. That's my job now that I'm retired.

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    • #3
      I just took the flapper off for the picture, all of them have flappers.

      My boat was a twin 470 original build so I suspect it only had 2 3" exhaust ports originally. The inners were added and matched at 3" probably to cut cost during the repower. As it has 3" mufflers, going to 4" thru hulls will not be cheap(that's on the very long term list). Mean time I'd like to just get rid of the only plastic thru hulls on the boat, hopefully with some "good used" bronze 3". I searched ebay and didn't have much luck so I was hoping someone else who had 470's might have a pair of these kicking around somewhere.

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      • #4
        Going to 4" exhaust thru hulls is not really needed in your case unless you also change elbow risers to 4" as well. My OEM were 4" so adding two more wasn't an issue since I was planning on new 4" elbows as well.
        "Joint Venture" 1978 28' twin 2017 Vortec roller cam 383/6.3L 350hp engines - You name it, I've either replaced it, restored it, rebuilt it or repaired it. That's my job now that I'm retired.

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        • #5
          My risers are 3.5" and then necked down with a fiberglass adapter... according to centek the 3" mufflers support 320hp, but that's in a perfect world. When riser replacement time comes it'll be new soft hose time as well and I'll look at upsizing everything as a package if the engine spec bears it out. Its far enough away I haven't started research yet there. Seems to me as the risers are 3.5", .5" more is unlikely to be any worse than .5" smaller though.

          Meantime... I hate plastic hull fittings and am on a likely fruitless search to match my existing ones just like when I was looking for the chromed bronze 1.5" thru hulls I wanted to match, ha.

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