how many lbs of thrust is equal to 1 hp?

Discussion in 'Outboards' started by deermaster, Nov 15, 2008.

  1. powerabout
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    powerabout Senior Member

    I would always like to see the current inflow degradation graphs
    Then you could compare them
     
  2. sandhammaren05
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    sandhammaren05 Senior Member

    Depends on speed and prop efficiency. Power (useful work/sec) applied to boat is P=TU/h where the h is the mechanical efficiency. For your case, consult the old tables by Gawn. See DuCane's book for the tables.

    In Greek alphabet h is eta.
     
  3. ron2017
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    ron2017 New Member

    Evolution 22

    Not sure if this thread is too old but here goes

    I have an Evolution 22 which I sail on the Black Sea which is non tidal

    I am looking for an outboard that will get me back into the marina once I get past the breakwater , if my main outboard was to fail

    I have been looking at a 62 lb electric motor which has 5 forward gears and 3 reverse

    What are the thoughts on whether this would suffice just to get me onto my mooring in the marina
     
  4. Manie B
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    Manie B Senior Member

    I have a 24v 86lbs thrust Newport which I am very happy with.
    I definitely would not go smaller.
    I would easily compare it to a 3,5 hp two stroke outboard or 4hp four stroke.
    We did many many many tests and my figures are pretty accurate.
     
  5. ron2017
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    ron2017 New Member

    Thanks manny , I am looking for literally some steerage in the marina should my main outboard fail , i am 1.5 ton evolution 22

    What size boat are you using it on
     
  6. Manie B
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    Manie B Senior Member

  7. ron2017
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    ron2017 New Member

    That's pretty good thanks for the feedback Manie
     
  8. ondarvr
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    ondarvr Senior Member

    I have a 24V 80 lbs thrust electric (and others), they are nowhere close to a 3-5 hp gas motor, my 2Hp gas motor would run circles around it. Don't fool yourself into thinking even a large electric trolling motor is close in power and thrust to the smallest gas powered motor.

    I'm not saying they won't move a large boat, just don't expect too much if there’s any wind or current.
     
  9. powerabout
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    powerabout Senior Member

    You also have an unknown difference between static thrust and moving due to current inflow.
    If you guess 50% of thrust is suction and 50% is from the pressure side you can see that once you are moving you lose lots of thrust.
    A 2 stroke that has a wide rpm range can make up for that.
    Hence if you compare static thrust with electric to 2 stroke even if the same the 2 stroke will move the boat faster in most cases as peak torque will be higher than when tied to the dock
     
    Last edited: Dec 30, 2016
  10. ron2017
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    ron2017 New Member

    I have found an 86lb motor which I could get

    What drawbacks did you identify on the 3 tone boat?

    Did it give you a good start stop capability when switching from forward to reverse and vice versa?

    eg: when reversing onto a mooring and putting into forward gear
     
  11. Joakim
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    Joakim Senior Member

    What did you test? Your electric motor has about the same bollard pull as a 2.5-3 hp OB, but it will not have the same thrust while the boat is moving.

    Look through this thread and you will find many measurements about that.
     
  12. Joakim
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    Joakim Senior Member

    Here are some bollard pull measurements I just happened to see: http://media.torqeedo.com/downloads/tests/sailing_today_072012.pdf
    So 88 kg (860 N) for Yamaha F9.9. Probably with 8 1/2 *9 1/4 propeller. Other 8-10 HP outboards got 82-94 kg and Torqeedo 4.0 100 kg.
     
  13. powerabout
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    powerabout Senior Member

    except for anchor handlers how useful is bollard pull to all of us boaters that are in boats that move?
     
  14. DCockey
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    DCockey Senior Member

    It looks like the standard Yamaha with the small prop was tested.

    As your earlier discussion pointed out bollard pull for outboards is frequently limited by propeller size, not power.
     

  15. pacific green
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    pacific green Junior Member

    I now have 3 seasons under the hulls of our 1964 Bill O'Brien Bobcat catamaran. We are 25.5 LWL and Displace 6000 lbs spread across a 14.5 foot beam. Powered by dual Rayeo 48v motors with advertised thrust of 195lbs each. The main propulsion battery are 16 400ah winston battery lifpo4 cells in series for roughly 20Kwh of energy storage. Buffering the batteries are 2160 watts of solar power producing from 0 to 30 amps and from 0 to 9 Kwh of solar or from 0 to 200 amp hours returned.

    The vessel is nothing short of amazing in all aspects on the water and she never ceases to amaze me. The Rayeo electric outboards are certainly worth entertaining especially if your running a pontoon boat. With over 600 videos of her plying the waters of the pacific north west the data clearly speaks for itself in terms of electric propulsion on boats. Of course I also buffer everything with a couple of honda 2000 generators and a couple of old golf cart chargers. I haul only 70 liters of gasoline. On any given day I use only 8 liters of fuel.

    The next time out on the vessel I will have four chargers allowing me to fully charge the batteries in around 4 hours at a 80 amp charge rate. Otherwise while underway I can then rotate props for 60 amps without touching the battery storage. Conceivably I could rotate prop for the full 4 Kwh rating of each motor or 8000 Watts. Seldom does the vessel require more than 2000 watts to operate.

    This year saw the addition of the second honda generator. This allowed each charger to produce 20 amps from each battery charger in eco mode. This was a drastic improvement over one generator powering two chargers for 30 amps. By making better use of the chargers and the generators we were able to do some pretty impressive sprints this season.

    On full batteries alone we can sprint across the straight of georgia over to gabriolla passage in the 4 to 5 kts range. Typically we have a range of between 70 and 100 km on a full battery usually arriving at our destination with enough power left over to cook or barbecue electrically. I can leave you the Solar Catamaran https://www.youtube.com/channel/UC6BAWH7F1cixqeoS1XlLYww link where I am working on putting up videos of us actually leveraging the power of the second honda this year and pushing close to the hull speed of the boat at 6.7 knots for hours at a time.
     
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