Doesn't rev out!!!

Discussion in 'Inboards' started by 202_ski, Apr 3, 2008.

  1. Jango
    Joined: Aug 2005
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    Location: Mid Atlantic

    Jango Senior Enthusiast

    ANYTHING you add to the back of the Boat will most likely "Push the Bow Down" and make it WORSE - more plowing. Tipping trim plates up, most likely will cause the boat to bounce or do nothing. Cavatation plates will only work, IF it enables you to move the Prop and Motor Back.
    You need to MOVE THE CG AFT. If your seating and controls are forward of the motor, move aft of the motor if posible. Good Luck
     
    Last edited: Apr 10, 2008
  2. lazeyjack

    lazeyjack Guest

    you could extend the lower hull section for 2 feet, like a pod
    then you would also have a platform for land fish
     
  3. kobus
    Joined: Mar 2008
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    Location: south africa

    kobus Junior Member

    can it be that u need a gearbox so that u take the load of the motor and make the prop spin faster ea more revs
     
  4. 202_ski
    Joined: Mar 2008
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    Location: Australia

    202_ski Junior Member

    The cav plates i put on covered the whole transom, extended out 30 cm and fixed a 12 degrees up, didn't seem to have effect. Same revs, same speed. When i have 2 or 3 people in the back seat and just me in the front it porpoises really bad continously. Does that mean it has no hope with the motor in its position?
     
  5. Jango
    Joined: Aug 2005
    Posts: 519
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    Location: Mid Atlantic

    Jango Senior Enthusiast

    The 12 deg up angle on the cavitation plate IS causing the Porpoising - same as a rocker shaped bottom.
    A Flat cavitation plate (NO up or Down angle) will ONLY work if you move the CG back. Otherwise it will push the bow down more. Use cavitation plate ONLY if you move prop (and motor) back.
    Moving the motor back is the BEST sollution. However,If you want to leave the motor in it's present location, you need to take weight away from, in front of the motor and add weight behind. - again, move CG aft.
     
  6. 202_ski
    Joined: Mar 2008
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    Location: Australia

    202_ski Junior Member

    Im going to move the motor fully aft and use a 4 by 4 transfer case as a V drive. But because standard transfer cases are not high ratio, i was thinkin of turning the transfer case upside down so the prop turns faster than the motor. Have you ever seen transfer cases used in boats?
     

  7. Jango
    Joined: Aug 2005
    Posts: 519
    Likes: 7, Points: 0, Legacy Rep: 63
    Location: Mid Atlantic

    Jango Senior Enthusiast

    Not real familiar with transfer cases, but you need to be careful with ratios. If the prop is turning real slow (relative to the motor speed), The Prop will need to be Huge, 16"+ Dia. (with a 2:1 gear). Turning the Prop very fast, It needs to be very small, 7" Dia. (with the same 2:1 turned upside down).

    Either of these conditions are not good, especially at lower speeds. Best if ratio is as close to 1:1 as possible, probably 1.5 :1 max or 1:1.5 (upside down)
     
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