Motor question

Discussion in 'Multihulls' started by SpiritWolf15x, Oct 17, 2010.

  1. SpiritWolf15x
    Joined: Apr 2010
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    Location: Vancouver, Canada

    SpiritWolf15x Senior Member

    Hey everyone, the normal motor on my Buccaneer 33 trimaran, a 30hp Tohatsu 2-stroke, decided it was going to refuse to start and then loose its leg oil... So until I get around to fixing it I'm down to using the only other outboard I have, an 8hp Tohatsu 2-stroke.

    What I'm wondering is if my little 8 has the power to push my boat. I only need it to do hull speed.

    Any help welcome,

    -Wolf
     
  2. Submarine Tom

    Submarine Tom Previous Member

    I'll bet she'll do 5 knots in still airs.

    -Tom
     
  3. SpiritWolf15x
    Joined: Apr 2010
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    Location: Vancouver, Canada

    SpiritWolf15x Senior Member

    I'm just concerned about it's ability to motor for 30 miles.
     
  4. pogo
    Joined: Mar 2010
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    Location: Germany Northsea

    pogo ingenious dilletante

    Wot ?
    Much too much.
    On my 35footer (with a deplacement in cruising trim of 2m3) i have a 15Hp Mercury 2-stroke with a standardprop , that`s enough.
    The motor is in a vertical tunnel in the cockpit, can be lifted with a tackle. No ventilation.
    While sailing the tunnel is closed by a an overlapping alloy plate, screwed to the outboard`s fin. Simple and effective.
    I guess that 8Hp aren`t enough for your boat, but, it depends on cubic and prop.
    A 10Hp outboard with 250ccm and two cylinders should have enough torque to drive your boat. The motor needs a prop with little less than standard pitch.
    Before i bought my Mercury 15Hp 2-stroke with 34kg , i had yamaha 4-stroke of 50 kg . That motor gave only half a mile cruising speed more and consumed only half a liter less---but cost twice the money.
    The Yamaha4-stroke is only a good motor when you push it at half throttle, then it consumes about 2 litres per hour. It`s a motor who`s gear and props are designed for 26┬┤waterline. The high thrust is only a nearly useless reserve for manouvering. u don`t use it while cruising.
    If u wanna push your boat to a hullspeeed of 7-8kn , with 3/4 throttle, then the motor consumes 3-3,5 litres, which is the same of a 2-stroke with 50% more nominal power that only costs the half .

    2-stroke with volume--light and power is the better way !

    pogo
     
  5. SpiritWolf15x
    Joined: Apr 2010
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    Location: Vancouver, Canada

    SpiritWolf15x Senior Member

    Yeah, the 30 is a bit or the "large" side for a motor, but it was the only motor we had at the time we got the trimaran. It's supposed to be on our 14' zodiac.

    The 8hp in question is off my late father's 35' racing cat, it managed to push that boat at about 7knots. I'm hoping for at least 6 with the tri.
     
  6. Landlubber
    Joined: Jun 2007
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    Location: Brisbane

    Landlubber Senior Member

    Do it, there is nothing to loose, and if the prop is suitable, the tri will certainly do 6 knots with the 8hp.
     
  7. Richard Woods
    Joined: Jun 2006
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    Location: UK, USA and Canada

    Richard Woods Woods Designs

    I assume your engine is at home

    It isn't on your engine bracket

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     
  8. SpiritWolf15x
    Joined: Apr 2010
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    Location: Vancouver, Canada

    SpiritWolf15x Senior Member

    No, it's at home right now. I brought it across with me when I took the powerboat home.
     
  9. oldsailor7
    Joined: May 2008
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    Location: Sydney Australia

    oldsailor7 Senior Member

    It should do better than that. Bad Kitty has two hulls. The B33 has virtually only one hull in smooth water. Less wetted surface.
    Should be alright. :D
     
  10. SpiritWolf15x
    Joined: Apr 2010
    Posts: 194
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    Location: Vancouver, Canada

    SpiritWolf15x Senior Member

    Thank you for all the input everyone.
     

  11. cavalier mk2
    Joined: Mar 2010
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    Location: Pacific NW North America

    cavalier mk2 Senior Member

    I used a 1957 7 1/2 hp evinrude for a year or two including looong trips on my 37' Nicol. It would cruise at 5 + knots except in a headwind where the prop slip would increase with the wind velocity. Your boat should do even better as it is lighter though you may not get the fun of repairing antique motors a few hundred miles from home ;)
     
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