What prop?

Discussion in 'Props' started by Poppajoe, Jun 13, 2006.

  1. Poppajoe
    Joined: Feb 2006
    Posts: 6
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    Location: South Wales, UK

    Poppajoe Junior Member

    Can someone help please?
    I have used various prop calculators and I am getting more confused.

    I have an 18ft Icelander fishing boat with a ford xld 1.8ltr, 60hp diesel through a Volvo 280 single prop drive.

    Details below, but I need to know what sort of revs I need to be running at.
    The prop calc suggests 14x12 or 15x15 depending what hull shape, tried both and with 15x15 she bogs down at 2300rpm at about 11 knots, with the 14x12 she runs at 2800rpm at about 14 knots.

    The calc suggested 17 and 23 knots respectivley, in fact with the details entered at their worst case senario I could not get a figure below 17 knots suggested.

    I would presume that smaller dia and larger pitch (ie 12x17) would reduce revs?

    I am not looking for any particular speed but want to obviuosly run at the highest possible. I am not concerned with fuel consumtion and do not mind wearing out an engine at around 500/1000 hrs.

    I can post a pic of boat showing hull if it helps?

    waterline length = 16ft
    max revs = 4800 (60hp)
    max torque = 108 NM @ 2500RPM
    drive ratio = 1.89:1
    boat weight = 1300kgs (max checked on weighbridge)
    max prop dia = 15"
    Hull form? = on plane would be very shallow "v" about 10 degrees?

    Any help would be much appreciated.
  2. Çemberci
    Joined: Apr 2007
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    Location: Istanbul/Turkey

    Çemberci Senior Member

    Propeler Size

    Limited Hull data the result is below:
    Diameter = 12.00 inç
    Pitch = 9.5 inç
    Dar =% 92.62 - 21 cm or 8.2 inç
    3 bladed
    Oktay Çemberci
  3. Jango
    Joined: Aug 2005
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    Location: Mid Atlantic

    Jango Senior Enthusiast

    I believe the HP given is Brake HP, which should be reduced by approx 25% to obtain Shaft HP.

    Using "Prop Calc" , the results are:

    Max Speed - 16 knots

    Prop - 12 x 10, 3 blade, D.A.R, 55% , 20% slip

    RPM should be close to 4800 unless Displacement is higher or motor not producing advertised HP.

  4. Çemberci
    Joined: Apr 2007
    Posts: 127
    Likes: 6, Points: 0, Legacy Rep: 133
    Location: Istanbul/Turkey

    Çemberci Senior Member

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