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  1. #1

    Default Shaft length question.

    Howdy all. I have a 2005 Carolina Skiff J14. The transom measured 16". It currently has a 15hp Honda and the shaft measures 17 inches. I might upgrade the motor to a new one and use the old 15 on a friends boat.

    Question is I see only 15" or 20" shaft options. Am I measuring my outboard correct at 17" from transom mount bracket to the keel just above the prop? I don't see any new motors with a 17" shaft.

    If my transom measures 16" I am thinking a short shaft is the way to go. But at 15 inches of shaft length that would put the keel above the prop at about a half inch above the bottom of the boat. Is this good?

    Thanks. I appreciate the help.

  2. #2
    Join Date
    Sep 2008
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    Hague, Virginia, USA
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    Default Re: Shaft length question.

    The anti-cavitation plate, which sits right above the prop (which I assume you are calling the keel) should be even with the lowest part of the hull at the transom.
    CHawk 25 DLX

  3. #3
    Join Date
    Sep 2010
    Location
    ontario
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    14,126

    Default Re: Shaft length question.

    A 16" transom takes a short shaft ( 15" ) motor.-----Folks are often confused about what the " shaft length " is and how it is to be measured on a motor.

  4. #4
    Join Date
    Sep 2008
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    Hague, Virginia, USA
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    3,813

    Default Re: Shaft length question.

    Basically shaft length is measured from the top of your motor mount to the cavitation plate. The link below illustrates.

    https://onlineoutboards.com/help.html
    CHawk 25 DLX

  5. #5

    Default Re: Shaft length question.

    Quote Originally Posted by chawk_man View Post
    The anti-cavitation plate, which sits right above the prop (which I assume you are calling the keel) should be even with the lowest part of the hull at the transom.

    Yes yes, anti-cavitation plate. No idea why I was calling it a keel. Anyway thank you for the responses. I ended up ordering a short shaft 20hp with a 15" shaft. From my measurements the ACP will be about 1/2 inch above the bottom of the boat. I have had enough responses saying the 15" shaft is the right motor so good to go.

    Do you all think that 1/2 inch is a concern? Before I go bolting it onto the boat should I shave down the transom a bit to get the ACP perfectly even or am I going way over board on this one?

    Thanks again everyone.

  6. #6
    Join Date
    Sep 2008
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    Hague, Virginia, USA
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    3,813

    Default Re: Shaft length question.

    It's a performance issue. The closer the anti-cavitation plate is to the bottom of the transom the better performance you'll get. You could install a manual jack plate on your transom which would allow you to move the motor up and down. Alternatively, you can install a hydraulic or electric jack plate which will an infinite number of settings and allows you to run in very shallow water. Below is a link to one of many that are out there...

    http://www.vancemfg.com/product-p/jp...hoCCokQAvD_BwE
    CHawk 25 DLX

  7. #7
    Join Date
    Sep 2008
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    Hague, Virginia, USA
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    3,813

    Default Re: Shaft length question.

    Well, someone was kind enough to send a PM and correct me on my terminology. I've always called the plate on an outboard that sits above the prop as an anti-cavitation plate. But I have been correctly informed that it's properly called an anti-ventilation plate.
    CHawk 25 DLX

  8. #8

    Default Re: Shaft length question.

    Quote Originally Posted by chawk_man View Post
    Well, someone was kind enough to send a PM and correct me on my terminology. I've always called the plate on an outboard that sits above the prop as an anti-cavitation plate. But I have been correctly informed that it's properly called an anti-ventilation plate.

    Funny. I have heard Anti-Cavitation plate. Never heard ventilation. I am no expert on the topic that is for sure. Maybe I will stick with that part that sticks out just above the prop.


  9. #9
    Join Date
    Dec 2006
    Location
    Chaumont Bay, N.y., USA
    Posts
    5,263

    Default Re: Shaft length question.

    Do you all think that 1/2 inch is a concern?
    Nope, it shouldn't be,.... 'n it might be ever so slightly Faster,.....

    A potential draw-back could be if ya get prop blow-out when turnin',.... possible, but unlikely as it is,....
    Any Grease is Better,... Than No grease at All....

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