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  1. #1
    Petty Officer 2nd Class
    Join Date
    Feb 2002
    Posts
    103

    Default 3 Blade vs 4 blade props

    I have a 350 Mag tournament ski, inboard, ( Sea Ray - Spitfire) and I am considering changing the prop from a 13 pitch 3 blade to a 4 blade. What do I need to consider, regarding pitch, when I go from 3 to 4 blades?

  2. #2
    Petty Officer 2nd Class
    Join Date
    Jul 2003
    Location
    Idaho
    Posts
    186

    Default Re: 3 Blade vs 4 blade props

    DETERMINING THE CORRECT PITCH:Adding 1 inch of propeller pitch will reduce wide open throttle rpm by 150 to 200. Subtracting 1 inch of propeller pitch will increase wide open throttle rpm by 150 to 200. If you are upgrading from a three blade to a four blade propeller, remember that a four blade propeller generally uses up to 50 to 100 rpm more than a three blade prop with the same pitch. 4-BLADE PROPELLER FACTS:Plane the boat faster than 3-blade propellers Keep the boat on plane at a lower speed Give improved mid-range speed at the same rpm as a 3-blade propeller Provide quicker acceleration than most 3-blade propellers Run smoother than 3-blade propellers Have better holding power in rough conditions are less likely to ventilate in sharp turns provide better low speed handling

  3. #3
    Seaman Apprentice
    Join Date
    Mar 2003
    Location
    Reno, Nv.
    Posts
    48

    Default Re: 3 Blade vs 4 blade props

    Better yet-look at Mercury's Stainless Steel High Five 5-blade. My 21ft SeaRay comes out of the hole real nice and smooth.

  4. #4
    Petty Officer 2nd Class
    Join Date
    Feb 2002
    Posts
    103

    Default Re: 3 Blade vs 4 blade props

    Graet advice - does that hold true for inboards(Ski boat) as well?

  5. #5
    Admiral tommays's Avatar
    Join Date
    Jul 2004
    Location
    long island
    Posts
    6,766

    Default Re: 3 Blade vs 4 blade props

    we have a correct craft and it is so compleaty different than and i/o boat because of the center mount engine and hull design thay really go through the water rather than rise up on plane to keep the correct ski wake i would talk to a prop shop that works on ski boats or people in the water ski comunitytommays
    If a dirty bottom slows you down what do think it does to your BOAT

    1970 Cal 29 Sea Fever
    http://cal29seafever.blogspot.com/
    1981 J24 Tangent 2930
    http://s565.photobucket.com/albums/s...%20for%20sale/
    Tommays
    Northport Ny

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