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  1. #1
    Cadet
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    Default Which is it, a long or short shaft Mercury?

    I am helping a friend replace his blown lower unit on a 1993 115HP Mercury in-line 4 cyl. My friend asked if he should switch to a long shaft or stick with what he has now. Frankly, I don't know if he has a long or short shaft now. First question, How do you measure the shaft length? I need to know which type he has now to order the replacement. Second question, How do you determine which lower unit would be right for a given boat? Is there some rule of thumb for shaft length to match a boat?Thanks,Mcgurk

  2. #2
    Supreme Mariner roscoe's Avatar
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    Default Re: Which is it, a long or short shaft Mercury?

    THe shaft length is listed in the model number.If you post it, someone can tell you, assuming he has the original lower unit on the motor.Also look here: shaft length picture




  3. #3
    Vice Admiral
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    Default Re: Which is it, a long or short shaft Mercury?

    where motor bracket sits on transom to the anti-ventalation/cavatation plate on L/U = current shaftlength.

  4. #4
    Cadet
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    Default Re: Which is it, a long or short shaft Mercury?

    Thanks for the responses. I won't be able to get to the boat before next weekend and I'll post the model number after that. I take it from both of the replies and looking at the diagram, that the normal shaft length should place the cavitation plate in-line with the bottom of the transom. Well, thats simple enough to measure. Thanks again. McGurk

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