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  1. #1
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    1971 mercury 800 short shaft

    Hello all. I have been working on a project 14 foot, I believe some kind of Glastron clone, and at one time last year I purchased a 800 merc that turned out to be a 71 short shaft with a kit to make it a long shaft. It needs quite a few wires replaced internally and I purchased another newer 800 for the current project while still planning on getting this short shaft put together and running for another project.

    I feel like I had read somewhere that short shafts at 80 hp or more is rare, Is this true? If this outboard ends up being a great runner, do I have something special?
    Last edited by fatlenny; 02-04-2023 at 09:58 AM.

  2. #2
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    The 800 and 850 short shafts were the G class motors for years. When the 850s came out I got a 800 off a race boat and put it on a small center console fishing boat for my wife. Those motors were great runners and dead reliable. My wife's 15' 6' fishing boat would run 58 mph all day and at cruise used less gas than a similar boat rigged with a 500. In my opinion those 66in 4 cyl motors were some of Mercury's best. Long shaft transom boats were much more common even in those days so short shaft motors tended to be used for race boats.

  3. #3
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    Long Shaft Luck

    Quote Originally Posted by fatlenny View Post
    Hello all. I have been working on a project 14 foot, I believe some kind of Glastron clone, and at one time last year I purchased a 800 merc that turned out to be a 71 short shaft with a kit to make it a long shaft. It needs quite a few wires replaced internally and I purchased another newer 800 for the current project while still planning on getting this short shaft put together and running for another project.

    I feel like I had read somewhere that short shafts at 80 hp or more is rare, Is this true? If this outboard ends up being a great runner, do I have something special?
    You might have luck on your side if the 80 HP has a 5 inch extension kit on it. Pull the gearcase and see if the drive shaft has a 5 inch stub shaft on the end where it inserts in the powerhead. If it does, remove the stub shaft and extension and you are back to an OEM short shaft. Bigger motors with short shafts had disappeared by 1980. Short shaft engines rare? Not really. But in 2023 you would be hard pressed to find any motor under 20 inches. Even 25 inches is considered normal. Boat builders have morphed their transoms to 25 inch. To my memory, Merc never made "extension" motors but provided kits to dealers instead.

  4. #4
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    Quote Originally Posted by WaterZebra View Post
    Pull the gearcase and see if the drive shaft has a 5 inch stub shaft on the end where it inserts in the powerhead. If it does, remove the stub shaft and extension and you are back to an OEM short shaft.
    Yes It does have the stub shaft, I figured the extension was a kit added at some point. I just need to find the next project boat for it or maybe plan on building a small one person boat for it.

  5. #5
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    Re 71 Mid does it have value.
    As a 71 year motor it could and most likely is the early model stud pattern. (not so valuable)
    If it has the later 72? plus stud pattern thats worth something to the right buyer. These mids take the 6 inline powerheads,
    so a possible 1500xs clone in the making.
    Last edited by JAFFA; 05-05-2023 at 08:18 PM. Reason: Clarification
    Peter Thomas

  6. #6
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    ...the extension kits were made by bay manufacturing, milan ohio. you could buy them through a mercury dealer, or direct from bay themselves. they are actually still in business. www.baymfg.com
    Last edited by FUJIMO; 05-05-2023 at 08:30 PM.

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