Can a ski boat be converted to use electric motors?

Discussion in 'Hybrid' started by briapete, May 22, 2008.

  1. briapete
    Joined: May 2008
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    briapete New Member

    My V8 inboard ski boat consumes a large amount of gas. With the current prices of gas it leads to the question of: Can my ski boat be converted to use electric motors? Could electric motors get the 2400 lb 19 foot long ski boat to 40 mph and still get a skier out of the water? Is this even a practical idea?
  2. Fanie
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    Fanie Fanie

    Yes, you can use electric motors,
    yes you can get that speed
    yes you can pull a skier
    No, it is totally unpractical.
    The cable to get three phase power to your boat is going to ruin everything !

    Sorry, couldn't resist :D

    The biggest electrical motors working off batteries could not nealy produce the same power as a V8. Someone is working on a replacement alternative right now but it is going to be a while yet.

    Best alternative would probably be to look at an outboard to replace the V8 with. Sorry again, but no easy cheap easy alternative.
  3. masalai
    Joined: Oct 2007
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    masalai masalai

    I am not an expert in anything, it appears to some, except drawing attention and expressing my view (some call it "throwing red herrings about" but),
    My understanding is that electric motors can deliver FULL torque from the start (power to pop the skier up), but lack the horsepower and top end revs to pull skiers and other stuff that a V8 of big outboard could do better without the need for a long 3 phase cable (Fanie has expert knowledge) or huge (heavy) battery bank and large charging capacity of a V8 engine powered generator.... which would probably need to be revved up to get the generator going before planting the electric motor throttles....
  4. DanishBagger
    Joined: Feb 2006
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    DanishBagger Never Again

    Hehe, one could go for Lithium-manganese batteries. But at 3000 euro per 77ah (at 25 volts) a pop, that would be rather expensive. The great thing about those batteries is that they can deliver their power even faster than li-ions, and many, many times faster than lead acids. The 77Ah weighs in at 18kg, btw (40lbs). Lithium ions/or manganese is capable of delivering almost all their power in a very very short time period, so if that was all that mattered, it shouldn't be a problem.

    With batteries like that you wouldn't have any problems even at full throttle. But the problem is, of course, for how long?
  5. alan white
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    alan white Senior Member

    Your real problem is not the price of gas but the habit of using huge amounts of power to have fun.
    Going electric is not the answer. Lifestyle is. Unfortunately, you and millions of others are now paying for fuel you've been consuming all your lives.
    It's never been cheap. It's just that the cost has been hidden until now.
    The best advice I can give you is to stop using so much energy in every form.
    Even battery powered things have to consume huge amounts of oil to be produced in the first place. An electric car uses as much oil to be produced as a gas car, which is at least as much as a gas car will consume in a lifetime.
    How about a kayak or a sailboat made from wood?

  6. Quietboats
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    Quietboats Junior Member

    Interesting take Alan and very well said. As for the origional question--the viability of high speed electric boats--The energy density of gas is from 80 to 250 times greater than that of a lead acid battery (depending on who's figures are being quoted and can someone here give a real answer to that?). New batteries are an improvement but nowhere near enough to justify any type of planing watercraft. I expect this hard fact will not change for many years. So "NO", you cannot sensibly ski with electric. Want to go fast on the water cheaply--buy a water slide. Gravity is still free.
  7. sparky_wap
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    sparky_wap Junior Member

    Yes, It is being done now!

    The issue is energy storage, not peak power. An electric motor the size (or weight) of the V8 will make the power to pull the skier. See the link above for an example.

    In the world of auto drag racing, some very small motors have been used to replace gas engines with great success. Look up white zombie

    I have been playing around with smaller PM motors to get a small boat on plane. My goal is to plane for at least 30 minutes on Lead batteries.

    I'm working through some prop ventalation issues now but should planing on a surface prop.


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  8. charmc
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    charmc Senior Member


    You're right, energy storage (batteries, capacitors, etc), is the limiting factor now for all electric vehicles. The Edison boat is neat.

    Electric power is an alternative form of energy conversion, but it's not the panacea so many proponents seem to think. There's no such thing as a free lunch, and, while electric motors are pretty efficient, electric power generation is not. Plugging into the grid to charge batteries means burning fossil fuel to generate steam to generate power, which must be transmitted long distances . Efficiency losses at every step. Solar or wind generation eliminates the fossil fuel component of generation, but still takes energy and raw materials to manufacture the equipment.

    Alan has a point; if we are concerned about improving the environment we need to work at reducing energy consumption, not simply changing the manner in which we consume it.

  9. sparky_wap
    Joined: Mar 2008
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    sparky_wap Junior Member


    My obsession with electric power (boats) is mostly due to living on an 'electric only' lake. I figured I could push the limits of 'electric'. I started my project several years ago with zero knowledge of boats. Now I realize its a bigger mountain to climb than originally thought. When I started, I thought I could plane a 400 lb boat on less than 2 HP.

    LI batteries will help with the energy storage but initially at a great price. When the energy densities get about 5x my Pb batteries I'll look into converting my Bayliner to electic.

    Grid power here is cheap and mostly nuclear with some coal. New nuke plant is in the works (Really!). I know all about the losses and the 'well to wheel' eff discussions. I'm not a tree hugger but think there are beter ways of doing things. I would spend more on gas going to fill up a gas can than I do charging my batteries.

    (photos of other electric conversions- not mine)


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