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  1. #1
    Cadet
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    Default Question on long shaft vs short shaft outboards?

    I currently have a 1986 Sunbird with a 115 outboard einrude with the 20" shaft. I'm wanting to upgrade the power level to a v6 150 evinrude but mostly all i can find are 25" shafts. My question is does this extra 5" make the prop hang below the bottom of the boat that much or is the mounting bracket that bolts to the boat 5" lower so therefore the prop location is the same? I hope I made my question clear, it's hard to explain in words.

    Thanks,
    Jason

  2. #2
    Lieutenant Commander
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    Default Re: Question on long shaft vs short shaft outboards?

    First off measure your transom and verify the length. ( from top of cutout to bottom of V ). If you are within a couple of inches then you could go with a longer shaft. The biggest issue using a longer than necessary shaft is the undue drag due to its length.
    Life may not be the party we hoped for, but while we are here we might as well dance

  3. #3
    Supreme Mariner Silvertip's Avatar
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    Default Re: Question on long shaft vs short shaft outboards?

    If they moved the mounting bracket down 5 inches you would still have a 20 inch shaft so a 25 inch shaft motor is longer than a 20 inch. The measurement is taken from the top of the transom bracket (where the motor would sit if sitting full down on the transom) to the AV plate. A motor with too long a shaft for the boat may also cause some adverse handling issues.

  4. #4
    Senior Chief Petty Officer Navy Jr.'s Avatar
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    Default Re: Question on long shaft vs short shaft outboards?

    Quote Originally Posted by Jason1955 View Post
    I currently have a 1986 Sunbird with a 115 outboard einrude with the 20" shaft. I'm wanting to upgrade the power level to a v6 150 evinrude but mostly all i can find are 25" shafts.
    Before doing anything, perhaps you should double-check that your boat is indeed rated to handle the additional 35 horses. That's quite an upgrade (30 percent).
    2008 Lund 1750 Fisherman
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  5. #5
    Honorary Moderator Emeritus tashasdaddy's Avatar
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    Default Re: Question on long shaft vs short shaft outboards?

    i would install a hydrolic jackplate.
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  6. #6
    Petty Officer 1st Class
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    Default Re: Question on long shaft vs short shaft outboards?

    last summer i did a boat that was on the short side of a 20in transom. apparently 19-21 in qualifies as a 20 in transom. then i put long shaft outboard on it which again a "long shaft" varies from 18-22 in depending on manufacture and motor that was on the long side. so in effect i had a 22 in shaft on a 19in transom. that extra couple of inches differance caused water to flow up the transom and into the boat when trying to get on plane. a mini jack plate solved the problem. so besides extra drag with the shaft too long you may have a problem with water coming up the stern if you don't use a jack plate to get it to the proper height. i was able to use a fixed jack plate so it was only about $60. i think the manual adjustable ones aren't real expensive. i agree with TD that a adjustable jack plate will solve your problem and give you the bonus of being able to fine tune your boat/motor combination.

  7. #7
    Cadet
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    Default Re: Question on long shaft vs short shaft outboards?

    Thanks guys for the input. This gives me some options to think about over the rest of the winter.

    Jason

  8. #8
    Captain
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    Default Re: Question on long shaft vs short shaft outboards?

    I mounted a 25 inch shaft Evinrude 150 on my 19' Renken with a 20" transom. I used the lowest set of bolt holes and it ended up with the AV plate about an inch above the transom. It worked fine. There's usually enough adjustment in the 25" shaft V4 and V6 motors to allow using them on a 20" transom boat. Since these are bolt on motors, the length isn't as critical as a clamp on motor where there's no built in height options.

  9. #9
    Supreme Mariner
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    Default Re: Question on long shaft vs short shaft outboards?

    Jason, Depending on the year of each motor, the gearcases may interchange. You may need to swap the midsection as well.

  10. #10
    Cadet
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    Default Re: Question on long shaft vs short shaft outboards?

    I have a 22 inch transom but the motor I have is a 20 inch. Will that put te intake too higgh?

  11. #11
    Chief Petty Officer ddrieck's Avatar
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    Default Re: Question on long shaft vs short shaft outboards?

    Quote Originally Posted by tashasdaddy View Post
    i would install a hydrolic jackplate.
    The OP doesn't need a hydraulic jack plate per say just an extension plate set that raises the outboard 5''. CMC makes such an extension and from what I have heard it is quality item to fix the problem he is having.

    Seen them here: http://www.dhcampingandfishingsupply.com/50012.html

    Regards,

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