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Thread: Fitting low water pick up to outboard engine

  1. #41
    phillnjack
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    well the half out the water = more speed is not exactly correct !!!!!!!!!

    The larger pitch is requiered simply becase the propeller is not fully in the water.
    if 30% of the prop is not in the water then its not being used to propel the boat in forward motion,so obviously it would require more pitch on the remaining blades to keep the speed up.

    i did have another look at the video and yes i was wrong the bullet is out the water sorry about that.
    at one point the cone is not in use at all !!!!!


    phill

  2. #42
    BRF Team Europe Member Per's Avatar
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    Quote Originally Posted by phillnjack View Post
    well the half out the water = more speed is not exactly correct !!!!!!!!!

    The larger pitch is requiered simply becase the propeller is not fully in the water.
    if 30% of the prop is not in the water then its not being used to propel the boat in forward motion,so obviously it would require more pitch on the remaining blades to keep the speed up.

    i did have another look at the video and yes i was wrong the bullet is out the water sorry about that.
    at one point the cone is not in use at all !!!!!


    phill
    "Half out= more speed" is true under the right circumstances. With a prop designed for it you cut your losses and thereby win speed

  3. #43
    phillnjack
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    ask any prop maker and he will explain it to you.
    the only blades working are those in the water at any given time.



    phill

  4. #44
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    Quote Originally Posted by phillnjack View Post
    well in the video above he is not that high at all.
    he is only running with the cav plate about 2 inches above the water.

    he says he is running 3.75 up, but being as he is using a jack plate as well ,he is only about 1 inch higher than me.
    mine is running with the cav plate above water line and im just on the top hole with no jack plate and no setback.

    he is nowhere near running on the cone, so i dont see how he could lose water pressure.
    The bullet on his engine is completely submerged, not even a glimps of it.

    I noticed he has a nosecone, and it looks like they make a realy big splash, a lot more than the normal bullet.

    so whats the advantage of these cones ? im begginning to think they are just a gimic that dont realy work.
    if they cause the water to go up the gearcase and away from the prop then they are obviously diverting water away from the prop .
    this would mean less thrust due to less water at the prop.
    If they are helping to raise the engine then they would not help with water flow due to the cone pressing down on the water. !!!!!!!!!!!

    now the vid above shows a jack plate with setback,nosecone, and a hydrofoil and he still only gets 70mph on
    a 13ft lightweight raceboat with a 130hp engine.

    something dont sound right, how comke all these race improvements yet not much speed.
    I could get that on my dory with 130hp engine let alone a racing boat.


    phill

    no not 70 this guy is running a little over 82 mph. Do a search on here and you will see more pictures of that 13foot biel and that motor is actually a stock 130 yamaha.

  5. #45
    phillnjack
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    if you go on youtube and see his video's you can see its not stock.
    he has a different leg to normal stock motor and a tube running to the transom for water.
    that is not stock,plus jack plate and a nosecone.

    its ok to say its a stock motor, But its not stock on the outside.
    This guy has spent best part of $1,000 already on mods for the engine.


    phill

  6. #46
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    Quote Originally Posted by phillnjack View Post
    if you go on youtube and see his video's you can see its not stock.
    he has a different leg to normal stock motor and a tube running to the transom for water.
    that is not stock,plus jack plate and a nosecone.

    its ok to say its a stock motor, But its not stock on the outside.
    This guy has spent best part of $1,000 already on mods for the engine.


    phill

    Sorry what I meant stock was I think he had said there is no performance mod to increase horse power to the powerhead itself but yes that lower unit I guess is considered a performance mod.

    Here's the link to more pictures man I wish I had the money to own this boat they sure do look like fun http://www.boatracingfacts.com/forum...ht=Biel+13foot

  7. #47
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    from 3 o'clock to 6-6:30 is the thrust and or push the rest is Drag, thats from 6-6:30 back around to 3 0'clock = drag, when you surface the prop you unload the drag. don't work on every hull

    Part one of "Secrets of the OMC Mod 50" : http://www.boatracingfacts.com/forums/showthread.php?t=2052

  8. #48
    phillnjack
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    so whats happening between 6 and 9 ?
    i realy cannot see that being right.
    there is no difference between 6 to 9 to cause a drag effect.

    have you got any proof of this ? or is this just your opinion on the thrust v drag of prop blades ?


    phill.........

  9. #49
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    well, see if can get you there with words, the deeper you go the more weight water has, the opposite it true as well, yes, you with me, at 6-6:30 the blade is now turnnin into lighter water, the next blade is now turnnin in and down it is now pullin harder than the blade leavin the water, at the point that the incomin blade over powers the outgoin blade,
    at that point the out goin is drag, cuzz it's in the way

    Part one of "Secrets of the OMC Mod 50" : http://www.boatracingfacts.com/forums/showthread.php?t=2052

  10. #50
    phillnjack
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    who told you that water gets heavier the deeper down it is ? they dont understand H2o to even think about that.
    Do you think a diver can swim faster at 10 feet than he can at 30 feet with the same amount of bouyancy ?

    Yes there is more water Pressure the deeper you go, but this realy dont even start to be
    measurable untill 15 inches down.
    In the first 12 inches of water, the pressure is still the same as atmospheric pressure,roughly between
    14.7 and 15 psi depending on where you live.obviously high or extreme altitudes are not the same

    I dont think i could ever be convinced about the 3 to 6 thrust and 6 to 9 all being drag.



    phill...

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