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Thread: Options for improving tunnel hull

  1. #1
    Member AK Ray's Avatar
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    Default Options for improving tunnel hull

    I picked up an old Roughneck 1655 tunnel hull this spring. The one with the tall (5.5"?) tunnel that works well with a prop. Then I picked up an older Honda 50/35 jet that needed major carb work. At the end of the summer I had the motor working finally and had the boat running well on Big Lake test runs.

    However, due to the loss of displacement with the large tunnel and the heavy motor it squats in the rear. I do have angled shims in place to give me extra tilt reducing the bow rise but that will not fix the squattiness at the stern.

    This leaves me with some hull modification decisions to make.

    A - Fill in the huge tunnel with an insert that is more modern in concept. Not as tall/deep and more like what Speciality Jets shows on their website for an optimum design. However, this won't help with all of the displacement issues and the heavy four stroke motor holding down the stern.

    B - Install pods and leave the huge tunnel. Install a flexible "deck" to capture water for the jet foot between the pods.

    After reviewing many of the posts on here I am tilting towards the pods. With the 50/35 the boat is kind of underpowered so it will never be a shallow water, tight and twisty creek running machine.

    Which shop in the Anchorage/Mat-Su area would you folks recommend for getting pods built and installed?

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    Quote Originally Posted by AK Ray View Post
    I picked up an old Roughneck 1655 tunnel hull this spring. The one with the tall (5.5"?) tunnel that works well with a prop. Then I picked up an older Honda 50/35 jet that needed major carb work. At the end of the summer I had the motor working finally and had the boat running well on Big Lake test runs.

    However, due to the loss of displacement with the large tunnel and the heavy motor it squats in the rear. I do have angled shims in place to give me extra tilt reducing the bow rise but that will not fix the squattiness at the stern.

    This leaves me with some hull modification decisions to make.

    A - Fill in the huge tunnel with an insert that is more modern in concept. Not as tall/deep and more like what Speciality Jets shows on their website for an optimum design. However, this won't help with all of the displacement issues and the heavy four stroke motor holding down the stern.

    B - Install pods and leave the huge tunnel. Install a flexible "deck" to capture water for the jet foot between the pods.

    After reviewing many of the posts on here I am tilting towards the pods. With the 50/35 the boat is kind of underpowered so it will never be a shallow water, tight and twisty creek running machine.

    Which shop in the Anchorage/Mat-Su area would you folks recommend for getting pods built and installed?
    You can simply have a shop weld in a plate to give you a smooth bottom, or if you really must have a tunnel, set it up the way you want.
    Having a tunnel on the back of the boat is going to severely increase drag as you are lifting a slab of water the size of your tunnel, this is why you have the squat problem. Pods may help, but you still are going to be lifting that huge slab of water which will dramatically slow you.
    Great spirits have always found violent opposition from mediocre minds. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence. Albert Einstein

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    Now that you have that anchor running well, consider selling it for a better power:weight ratio motor.
    Great spirits have always found violent opposition from mediocre minds. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence. Albert Einstein

    Better living through chemistry (I'm a chemist)

    You can piddle with the puppies, or run with the wolves...

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    Does your boat still have the original water logged foam in it? I have the same boat with a 55 Johnson two stroke and I can tell you it will run an inch of water with four guys and their day packs and rifles! But i striped all foam and any extra aluminum that was not in place as any sort of structural support. Everyone fights over it when i take it on a trip because it is so much fun to run...


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    Member AK Ray's Avatar
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    Quote Originally Posted by Yentna_rat View Post
    Does your boat still have the original water logged foam in it?
    The only foam is in the benches and probably in the two back boxes in the stern. Its all above the water level that comes in with the rain. The foam in the benches is dry. I have not bothered to open up the two stern boxes.

    There is a lot of extra metal since the prior owner (an older man in his 70's) had a full diamond plate floor installed along with a nice metal removable fish box up in the bow. I like it, but it does need to come out if I really want to get the most out of the boat.

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    Fill in the tunnel with an insert and move your tank and battery up front. I have a jet tunnel and added pods later which are great but are good when it's just me but less necessary when I have someone else or a load in the boat for proper weight distribution.

    Sobie2

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    I have never heard that tunnels increase drag? Just saying I have never heard that before.
    You lose the amount of displacement that the tunnel represents, maybe equal to 3 gallons of water at 8.34 pounds per gallon or ~25 pounds of displacement, (depending on the size of the tunnel).......

    As far as lifting the water goes goes, the water is simply flowing into a area of low pressure...............
    You do lose a small amount of planing surface, but a well designed tunnel flattens out at the end and you gain some of that back. If the tunnel is not flat it can cause some grief, especially if it angles down, even a few degrees and it can act like a big trim tab and push the bow down casuing bow steering. Better to keep flat or even angle up a degree or two. If the tunnel exits the transom at very much of a angle it makes it diffucult (next to impossible) to get the jet set right. the jet swings thru a arc and the water needs to be directed at the foot.

    I like having a tunnel but maybe someone that can read water better would find it unnecessary, I still manage to beat up the jet foot some. I probably would have done a lot more damage w/o a tunnel, but maybe the jet foot is a lot tougher than I give them credit for............



    Quote Originally Posted by Nitroman View Post
    You can simply have a shop weld in a plate to give you a smooth bottom, or if you really must have a tunnel, set it up the way you want.
    Having a tunnel on the back of the boat is going to severely increase drag as you are lifting a slab of water the size of your tunnel, this is why you have the squat problem. Pods may help, but you still are going to be lifting that huge slab of water which will dramatically slow you.
    “Nothing worth doing is easy”
    TR

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    The pods will cost some to get them fabbed, plenty of info on the forum about pods, to date they have been the best improvement I have made on my boat. Maybe the tunnel you have will work well with pods? I have heard both positive and negative concerning jets on prop tunnels.....? so no help there, but if you do have pods built make sure and leave enough room for a proper jet tunnel. Suprised to hear the 50/35 squats the boat so much? Is it a 55" bottom?

    Quote Originally Posted by AK Ray View Post
    I picked up an old Roughneck 1655 tunnel hull this spring. The one with the tall (5.5"?) tunnel that works well with a prop. Then I picked up an older Honda 50/35 jet that needed major carb work. At the end of the summer I had the motor working finally and had the boat running well on Big Lake test runs.

    However, due to the loss of displacement with the large tunnel and the heavy motor it squats in the rear. I do have angled shims in place to give me extra tilt reducing the bow rise but that will not fix the squattiness at the stern.

    This leaves me with some hull modification decisions to make.

    A - Fill in the huge tunnel with an insert that is more modern in concept. Not as tall/deep and more like what Speciality Jets shows on their website for an optimum design. However, this won't help with all of the displacement issues and the heavy four stroke motor holding down the stern.

    B - Install pods and leave the huge tunnel. Install a flexible "deck" to capture water for the jet foot between the pods.

    After reviewing many of the posts on here I am tilting towards the pods. With the 50/35 the boat is kind of underpowered so it will never be a shallow water, tight and twisty creek running machine.

    Which shop in the Anchorage/Mat-Su area would you folks recommend for getting pods built and installed?
    “Nothing worth doing is easy”
    TR

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    Member AK Ray's Avatar
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    AKgramps, I have not measured the bottom width, but it is nearly as wide as the top. This old hull has nearly vertical very tall sides. With the center console, battery and small fuel tank there is a lot of weight in the stern. I have let my 85 pound kid drive the boat and I and the dog staid up on the bow. This did allow for more of the stern to come up out of the water, but still some squat to the stern.

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    Quote Originally Posted by AK Ray View Post
    AKgramps, I have not measured the bottom width, but it is nearly as wide as the top. This old hull has nearly vertical very tall sides. With the center console, battery and small fuel tank there is a lot of weight in the stern. I have let my 85 pound kid drive the boat and I and the dog staid up on the bow. This did allow for more of the stern to come up out of the water, but still some squat to the stern.
    Pods will help a bunch, a 16 footer can be a lot of fun, you will be able to go almost anywhere, but how far and how much you carry would be limited. It may not be worth the trouble & expense to build pods, unless its something you can do yourself.
    Maybe consider running it as is, move what you can forward to get better weight balance, maybe even move the console, lighten it as much as possible.
    I would leave the tunnel as is until you try it out...........
    “Nothing worth doing is easy”
    TR

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