ventilation propeller problem

Discussion in 'All Things Boats & Boating' started by dimitriosa, Dec 5, 2005.

  1. dimitriosa
    Joined: Dec 2005
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    Location: greece

    dimitriosa New Member


    i have an inflatable boat 7,oo meters with a mariner long shaft outboard 200hp.(1996 model)
    i recently put a static cmc aluminum braket (9 inch) and i have a problem with my 21 aluminum propeller...when i rich the 5400 rpm its taking air and goes at 6000-6500 rpm....(trim all down)
    i have put the engine 7.5 cm highter than before (the bracket) and i CANNOT lower the fix my problem..
    so i either change the motor from a long shaft to an extra long (and iearn 12.5cm )but its an expencive way or i am looking for something else like the permatrim solution (M9?)
    i forgot to tell you that i have no trim anymore (when i touch the trim button to rise the motor even 1 cm ,the proptakes air ...or even i turn the boat a litle the prop takes air...)
    i thing i need 4 cm lowring the motor to have no problem but i CANT.....)
    thank you in advance
    dimitrios archolekas
  2. ABoatGuy
    Joined: Aug 2004
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    Location: LeftCoast

    ABoatGuy Member

  3. marshmat
    Joined: Apr 2005
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    Location: Ontario

    marshmat Senior Member

    This is probably far more expensive and complex than you're thinking of, but have you looked at a hydraulic jack plate? Might help get the motor down a bit....
  4. dimitriosa
    Joined: Dec 2005
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    Location: greece

    dimitriosa New Member

    i cant put an hydravlic jackplate cause (i fotgot to tell you that the excaust is really close to the water so i cant get down) its a long shaft motor to an extra long trancom.....
  5. cyclops
    Joined: Feb 2005
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    Location: usa

    cyclops Senior Member

    Why did you put the motor 7.5 cm higher to get a deeper propellor?-------Does the boat look level from outside of it with a normal load or does it ride front down?
  6. dimitriosa
    Joined: Dec 2005
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    Location: greece

    dimitriosa New Member

    before the bracket (9 inch back) it was balanced...after the bracket in a calm sea and not running seems to be overloaded back...the excaust hole is close to the sea (4 inches now,,) so i cant go one hole down to earn one inch....
    iam afraid of water in the pistons....
    i made it to earn the place infront the motor head where i put a refreferator for fishes.....
  7. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    Get rid of the bracket, and build a platform over the engine for the fish box.

  8. Captain T

    Captain T Guest

    You can take it a wee bit slower, stay on your plane.
    Most waste fuel by taking it to WOT or near it, the loss in mph is negligible anyway as long as you maintain a plane.
    Put her on plane, back off till you lose the plane, then find the rpm that 'JUST' keeps you on the plane; save mucho fuel and will not eliminate the ventilation, not on turns, but will discourage it big-time.
    Cavitation is much more serious, prop damage.
    Captain Lee
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