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  1. #1

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    Question Complete Breakdown of How a Ski Functions

    Alright guys, I'm prepared for the bashing and ridicule, but the search function has left me with bits of information that don't complete my understanding of how a pwc and its engine work.

    For me to better repair my ski, I need to know the ins and outs of it.

    What I've gathered so far is...

    the combustion engine functions like any other, fuel fed from carbs (EFI if you're fancy) into cylinder where compressed air is mixed and combusted creating the power stroke turning the driveshaft, turning the impeller, taking in water and shooting it out the back. Bam, you go forward.

    Now the water taken in is coming through the intake grate, yes? The impeller is just inside the intake grate?

    then it travels through a pump shoe? And out the steering nozzle?

    Now, the water that cools the ski is not the same as the water being forced out the rear for propulsion right? And if so, where does the cooling water come from and where in the engine does it flow.


    Please fill in the gaps with part names and functions and rectify my mistakes.


  2. #2

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    Also, would love some input on the handling aspects of a ski. On land its about suspension and tires. On water it seems to be about hull angle, and ride plate?

    What characteristics of the ride plate will alter your handling abilities one way or the other?

    How do trim tabs play into the equation?

    And how does adjusting sponsons alter the ride?


    Again, i know this thread is just soaked in newb juice but i want to know everything i can and telling me to search more and read more is bogus. (I've been at it for weeks now!)

  3. #3
    I wanna go FAAAAASTer!! CDW78's Avatar
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    Here's a good read for you - Answers most of your questions!
    http://adventure.howstuffworks.com/o...watercraft.htm

  4. #4
    mudslanger's Avatar
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    In a nut shell you are not far off. The engine cooling gets its water from the jet drive. The static pressure building up in the stator pushes water through cooling lines interning the engine.

  5. #5

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    Quote Originally Posted by CDW78 View Post
    Here's a good read for you - Answers most of your questions!
    http://adventure.howstuffworks.com/o...watercraft.htm
    Thanks for the link! I had already read that one though. I'm looking for more detail and insight on specific parts and functions. But I do appreciate the input guys.

  6. #6

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    Quote Originally Posted by mudslanger View Post
    In a nut shell you are not far off. The engine cooling gets its water from the jet drive. The static pressure building up in the stator pushes water through cooling lines interning the engine.
    That makes sense. Does water flow through the exhaust..?

  7. #7
    Almost's Avatar
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    Quote Originally Posted by yamygp1200 View Post
    Quote Originally Posted by mudslanger View Post
    In a nut shell you are not far off. The engine cooling gets its water from the jet drive. The static pressure building up in the stator pushes water through cooling lines interning the engine.
    That makes sense. Does water flow through the exhaust..?
    Yes and no. The exhaust is water jacketed down to where it meets the water box. So yes the exhaust is water cooled but its not in the exhaust itself until it reaches the water box. Hope that makes sense. A service manual or the parts schematic at the top of the page were you buy oem parts will probably give you a much better idea of what's going on.

  8. #8

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    So what is a pump shoe and why should i seal it?

  9. #9
    mudslanger's Avatar
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    Your jet drive on your ski is a big water pump. and if it is sucking air it is not sucking in water like it is suppose to so it can not propel your ski like it is designed to. the water inters the pump through the pump tunnel/pump shoe.

  10. #10

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    Quote Originally Posted by yamygp1200 View Post
    So what is a pump shoe and why should i seal it?
    The pump shoe is the flat piece of aluminum that is between the intake grate and the ride plate. It has many functions. We will just discuss the relationship between the shoe and cavitation.

    The portion of the shoe that is interior to the hull helps to shape and direct the water efficiently into the impeller so that the impeller can process (accellerate) the water efficiently.

    Yamaha did a poor job of sealing between the shoe and hull where the shoe and hull touch nearest the ride plate. They put a spongey type seal between the shoe and the hull. It quickly gets blown out when exposed to high water pressure. People remove the shoe and seal the whole mateing surface of the shoe to the hull, but the critical portion on the shoe is closest to the stern where the shoe, hull and ride plate meet. If you ever ride behind a GPR, you will see all of the water disappear between the thrust nozzle and ride plate upon take off. It is not a stretch to imagine air being sucked into the intake from the back of the boat where these three components meet.

    I would recommend 3M 4200 semipermanent sealant or Attwood marine polyurathane sealant (@ Walmart). The 3M 5200 is SUPER strong permanant sealant. If you use this stuff, it will be extreemly difficult to remove at a later date. It is just that, permenant.

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