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Thread: 13' tunnel hull motor height

  1. #1
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    Default 13' tunnel hull motor height

    I have been working on this boat for a while and I'm just starting to test it on the water. The other day I took the boat out after moving the gas tank to the front and lowering the motor a little. I hit 55mph pretty fast. I was driving strait and then all of the sudden the back of the boat started trying to come around. I was able to correct it but, it was definitely a scarry feeling. My question to yall, is this caused by the motor being too high or weight distrubution? or both? how high should I run my motor on a tunnel. The boat is powerd by an evinde 75hp with a 12.5x23 cleaver. Here is a pic of the inside. Let me know what other info yall need.
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  2. #2
    Team Member Detroit Whitey's Avatar
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    sounds like its the prop maybe try a round ear.im sure somebody will chime in on this

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    Stanley Henderson shenders's Avatar
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    Default Braking loose

    Sounds like you may be a little high with the motor. Drop an inch and see what happens.
    Your going to need to work with your set up,,, up / down------ in /out.

  4. #4
    Dago fast
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    Default Prop walking

    Quote Originally Posted by shenders View Post
    Sounds like you may be a little high with the motor. Drop an inch and see what happens.
    Your going to need to work with your set up,,, up / down------ in /out.
    Put your boat on a 4 inch plastic abs pipe and check where the center of gravity is. It should be right under your butt. Then move weight and things so thats where the center of gravity is. Then start with the prop shaft even with the bottom of the boat. I assume you have power trim.

  5. #5
    BRF Team Europe Member
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    What gearcase ? pics ?
    Argo Cat 18 - Sold
    Merc 2.4EFI/CLE - Sold

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    U.K. J 250 - Euro JT250 Techteam's Avatar
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    Um.... change those steering pulleys before you have a massive accident

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    Take a photo of your current prop shaft location in relationship to the sponsons/tunnel and post...the more the better...that will answer a lot of questions here....give the dimension of the centerline of your propshaft to the bottom of your sponsons...(above or below) I have had simlilar transom walking issues when the propshaft was too LOW in the water, until I raised it 2" above the bottom of the Sponsons...all tunnel/gearcase designs will act differently however....gg

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    AeroMarine Research Jimboat's Avatar
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    Quote Originally Posted by tunnelvision07 View Post
    I hit 55mph pretty fast. I was driving strait and then all of the sudden the back of the boat started trying to come around. I was able to correct it but, it was definitely a scarry feeling.
    what is the weight of the boat/setup? Do you have a pic of the boat while running?

  9. #9
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    steering cables and pulleys have been ordered already i knew the ones i have are not great. im not sure of the boat weight but its pretty light though. i have the nitro gear case with no power trim. how exactly do i put the boat on the pvc pipe? do i put it accross the trailer under the boat? i will post pics of motor height with measurements this afternoon. i just realized i posted this in the wrong section sorry about that.

  10. #10
    Team Member sheuninck's Avatar
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    Default 1 5/8"

    the sst60 manual says start with propshaft centerline 1 5/8" above sponson pad.

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