Propeller option for Minn Kota trolling motor

Discussion in 'Boat Design' started by Superamib, May 25, 2018.

  1. Superamib
    Joined: May 2018
    Posts: 1
    Likes: 0, Points: 1
    Location: Switzerland

    Superamib New Member

    Hi Everyone,

    This is my first post on this forum, so I apologize if this is posted on the wrong forum or already covered on another thread, I searched the forum a little but I found way too much technical information for my level of understanding ... sorry

    I just bought a Minn Kota trolling Motor (C2 55 lbs) to power an old wood sailboat.

    I'm trying to understand what would be the best propeller design for efficiency. I've tried several tools to assess the best prop design and was under the impression that it would require a 7 inch dia. prop with about 4 inch pitch at 1850 RPM

    What I don't understand is that the actual prop on this motor is a two blades about 10.5 inch dia. and 4 inch. pitch.

    With the 600W power from the motor it seems unlikely to reach the required RPM with such a large prop ....

    What would be the best choice ? Keep the actual prop knowing that the motor will pretty much run at half the RPM or change the prop for a smaller one and target the initial 1800 - 2000 RPM ?

    Thanks
     
  2. Blueknarr
    Joined: Aug 2017
    Posts: 632
    Likes: 93, Points: 28
    Location: Colorado

    Blueknarr Senior Member

    Welcome

    The engineers on this forum need much more information on your boat (size, displacement, hull form, ect) before giving informed useful advice.

    I'm a painter not an engineer. So my uninformed advice is to try the prop you have.

    How does it push your boat? How long do the batteries last?

    Test to find out what the actual problems are. Why fix it, if it ain't broke?
     
  3. JSL
    Joined: Nov 2012
    Posts: 743
    Likes: 37, Points: 28, Legacy Rep: 41
    Location: Delta BC

    JSL Senior Member

    good advice
    some boat specs would help.
     
  4. BlueBell
    Joined: May 2017
    Posts: 720
    Likes: 71, Points: 28
    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    Is it a 6 foot wooden sailboat and a lithium battery or a 55 foot wooden sailboat with 8, 6-volt golf-cart batteries?
    With the information given, I'd say keep the prop it came with... or maybe it didn't come with a prop...
    More info is needed.
     

  5. portacruise
    Joined: Jun 2009
    Posts: 1,060
    Likes: 21, Points: 38, Legacy Rep: 218
    Location: USA

    portacruise Senior Member

    Hi, Superamib:
    Troll motor props are designed for bass boats. The goal of the prop is low-medium top speed with high thrust, and weed free performance which sacrifices efficiency and top speed. You can read on the link below about what can be done to improve efficiency: Efficient electric boat https://www.boatdesign.net/threads/efficient-electric-boat.27996/page-28 post #407 also previous posts by McDenny. Another chap also worked on this and found the putting a fairing on the troll motor down tube raised efficiency quite significantly.

    PC
     
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