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  1. #1
    blackvr's Avatar
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    3 blade vs 4 blade. who can break it down for me

    i still dont understand. i have done all kinds of searches of 3 blade vs 4 blade but can never get a great answer. all i ever hear is that 4 blades are faster up top. but why are they? it doesnt make sense. i know that they are from my own experience but my friend always tells me that a 3 blade is faster up top because it has less blades, therefore the water isnt blocked as much. plus on boats, dont they use less blades to go faster from my understanding. i just want someone to explain to me why. i have a 3 blade in my ski now and it is about 1.5 mph slower but, what im asking is if you have a 450-500hp ski, will the tables turn meaning the 3 blade will be faster? like if you have a 3 blade pitched to a 17/24 how the heck would you be able to bend a 4 blade far enough to match it?


  2. #2
    b_dolla44's Avatar
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    X2^^^ i've wondered the samething... someone shed some light on this topic please...

  3. #3
    And I would like to know is three blade 15/21 equal with four blade 15/21?

  4. #4
    Orlando Shark's Avatar
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    From my understanding: a 4 blade you can only bend so much before you can't anymore and will usually be faster with the same pitch. The 3 blade you can get better acceleration and be able to bend it a little more then a 4 blade and that's where the 3 blade is "faster".

  5. #5
    Orlando Shark's Avatar
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    Quote Originally Posted by JayErola View Post
    And I would like to know is three blade 15/21 equal with four blade 15/21?
    The 4 blade should have a little more top speed but the 3 blade should have better acceleration having the same pitch.

  6. #6
    blackvr's Avatar
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    Quote Originally Posted by ImAShark View Post
    The 4 blade should have a little more top speed but the 3 blade should have better acceleration having the same pitch.
    yes but a 15/21 3 blade is a steeper prop then a 15/21 4 blade. so if you have a ski reving to lets say 8500 rpm equally with both props being a 15/21 then the 3 blade should out perform the 4 blade in top speed. is this correct? btw the prop i have in my ski now is a 16/22 3 blade. i took out a 15/25 4 blade. when i had the 4 blade in i did 90mph at 9200 rpm and with the 3 blade i did 88.3 at 8850 rpm. So im thinking that if i increased my hp to spin the prop faster to 9200 rpm then the 3 blade will be faster then the 4 blade while having less pitch.. im i nuts or is this making any sense to anyone else?

  7. #7
    West Texas RXP skoepp's Avatar
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    what applies to a boat (out board prop) does not apply to our pumps.
    Most yield higher top end with 4 blade at same rpm with our pumps.
    Your findings in your post below seem correct.
    You should gain more top end when add enough power with the 3 blade to run that same 9,200 rpm.
    I bet speed would be similar but at the same time with that extra power you would be on limiter with the same pitch on 4 blade so in theory you could add more pitch to 4 blade and gain more speed.



    I think there are some threads on this topic and why somewhere????

  8. #8
    speedskixp's Avatar
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    Quote Originally Posted by blackvr View Post
    yes but a 15/21 3 blade is a steeper prop then a 15/21 4 blade. so if you have a ski reving to lets say 8500 rpm equally with both props being a 15/21 then the 3 blade should out perform the 4 blade in top speed. is this correct? btw the prop i have in my ski now is a 16/22 3 blade. i took out a 15/25 4 blade. when i had the 4 blade in i did 90mph at 9200 rpm and with the 3 blade i did 88.3 at 8850 rpm. So im thinking that if i increased my hp to spin the prop faster to 9200 rpm then the 3 blade will be faster then the 4 blade while having less pitch.. im i nuts or is this making any sense to anyone else?
    You are making sense. It takes more power to turn the 3 blade. If you have a 15/21 3 blade turning 8800 it will be faster than a 4 blade 15/21 at 8800. Thing is that the motor turning 8800 with the four blade would not be able to turn the three abviously. I think once you are making 400+ horsepower the 3 blades would be the way to go,

  9. #9

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    who here has ever used a tap for threading a hole? for every revolution, the more blades/flutes you have, the less cutting is done per blade/flute. less cutting done per blade/flute = less force required to cut the material. same principle for the props. more blades = less water cutting per blade = less power required. as for which is faster, well i would think that resistance plays a role in it too. more blades = more resistance, so if your motor has the power to spin a fewer number of blades, it should be faster. that's my backwoods logic on the subject, so it might not actually be the reality of the situation. it's just what makes sense in my head, lol.

  10. #10

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    Quote Originally Posted by got wake? View Post
    who here has ever used a tap for threading a hole? for every revolution, the more blades/flutes you have, the less cutting is done per blade/flute. less cutting done per blade/flute = less force required to cut the material. same principle for the props. more blades = less water cutting per blade = less power required. as for which is faster, well i would think that resistance plays a role in it too. more blades = more resistance, so if your motor has the power to spin a fewer number of blades, it should be faster. that's my backwoods logic on the subject, so it might not actually be the reality of the situation. it's just what makes sense in my head, lol.
    3 blades shine on the bottom end and the 4 blades shine on the top-- each has to be pitched for optimal results. If you are doing speed runs or just high speed cruising you will most likely prefer the solas 4 blades. I have a few of each, but I plan on keeping the 3 blade in most of the time for my riding style and adding more boost and fuel to get the top speed that I like.

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