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Vented tunnel hull question

Discussion in 'Boats, Blinds, & Gadgets Forum' started by freefall, Dec 4, 2017.

  1. freefall

    freefall Elite Refuge Member

    Aug 22, 2012
    Lodi, CA
    I was looking at a new/used boat and it has a tunnel hull. Its a 1754 with a 60hp 2 stroke prop. The motor height is lined up with the tunnel, not the keel, so it rides high in the tunnel.

    The owner says he gets 31mph unloaded. That leads me to believe that something is off. With as light as the hull is a 60 should blast that thing into the 40s with ease...

    My question is, if the tunnel is to blame could venting it help gain the top end back?

    He also has a jet for the outboard but states that the jet sits too low and cannot get enough clean water to be used without raising the transom.

    I suggested a jack plate but with the offset it could loose clean forced water by being set back to far.

    Thoughts and suggestions?...
  2. calling4life

    calling4life Elite Refuge Member

    Feb 10, 2009
    Tunnel could be part of the issue, yes, venting does help, yes. Also, if you're running the outboard high and that takes precedence, the prop is shaped for that and potentially could be costing top end there as well, I know mine did.

    Yes, buy a powered jackplate, if I was better on a computer I'd post Ott Defoes tunnel, when he has it in "super shallow" mode, it has a power jackplate on the back of a power jackplate (12" of height adjustment), the motor is way behind the transom as well, but he'll run it all day in 3" of water. I'd also bet my house that because of the leverage of that outboard being so far back and the fact that he has no pods on the back of that 1860, that the arse end sags way down in the water when not on plane. So stay on plane, or run pods/recessed transom.

    Anyways, sure, venting the tunnel can help, monkeying with prop cup/pitch/blades etc... could as well, boat setup could also be a player. As far as the worry with the motor being too far from the transom, as I understand it, it can, in extreme cases be a problem, but 99.9% of the time you wont get it there, as you can see if you google the picture of Ott's boat with the double jackplate. However, a good solution to help, buy a compression plate, boatright, trans sports boats, manta ray (if they're still made), a good compression plate is essentially an extension of the tunnel, it catches and keeps the water where it needs to be, also helps with steering control. Mine keeps water around the prop area so well that it cut my exhaust noise down drastically too, good compression plates are worth it.

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