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Thread: Jet tunnel roof extension between pods?

  1. #1
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    Default Jet tunnel roof extension between pods?

    I've got a Sea Ark 2272 Super Jon with a Mercury 135 Optimax (both jet and prop capable with CMC transom power lift) now undergoing several performance mods. I'm looking for advice from the many extremely knowledgable and helpful folks on this forum, regarding extending the roof of the jet tunnel (tunnel install currently in work, not a factory tunnel hull) 10" aft to close the gap between transom and jet leading edge intake left from the 10" setback on power lift. My reason for wanting to extend the tunnel 10" aft of transom and between new float pods (also part of current modification) would be to close that gap then left between pods. Has anyone here done this when running both a jet tunnel hull (as opposed to boxier prop tunnel) with float pods installed as well? Doing so will close the gap between the trailing edge of the tunnel/transom and the front of the jet foot, which also increases "flat water" available to the jet. I'll post pics as they become available, but hopefully I am explicit enough here for solicited input from those "in the know". Thanks in advance and "cmon spring" already, enough of this pathetic quasi winter/ breakup condition!

  2. #2
    Member Akgramps's Avatar
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    Yes, extend the tunnel as far back as possible and connect the side of the tunnel to the bottom of the pods. Then use a piece of rubber (belted) bolted to the top and sides of the tunnel, Bring the rubber back over the top of the foot as far as possible. You can make a circular cutout in the roof of the tunnel for the foot leading edge to swing.

    I have found I can run the leading edge of the foot almost a inch above the top of the tunnel w/o any cavitation.
    I have a power trans lift with 7" of stroke, I have it set so when I run the lift all the way up its above the tunnel. This allowed for some adjustment. Seems the CMC has less travel...?

    Very important to make sure the roof of the tunnel is parallel to the chine or even slightly uphill. The bottom of the pods should angle up slightly as they extend to the back. This is my experience on my boat. However if the roof is angled the wrong way it will push the bow down. Same with the pods as they are essentially a extension of the planing surface that is behind the motor.

    I will try to get a pic of the flap this weekend.

    I have raised the top of the pods 4" since I took this photo.





    Here is picture in action, looking down, you can almost see the inside of the port side pod, the rubber, bolts on the side of the tunnel and the angle on top of the tunnel. You can see where the bottom of the pod extends over to close off the tunnel..
    Hope this helps



    PODS.......BEST MOD YET.....!
    “Nothing worth doing is easy”
    TR

  3. #3
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    AKGramps, I sure appreciate your knowledgable input! Please check your inbox for a PM from me.

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