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  1. #1
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    Compression #'s on 225 Pro XS 4-stroke?

    Looking at a used boat at a dealership, what compression should a 2020 225 HP Pro XS Four stroke have on each cylinder?
    Last edited by MikeBelter; 01-23-2023 at 09:42 AM.

  2. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #2
    Compression is almost never used with these engines due to the Smart-Start system. LEAKDOWN testing is a far more accurate measure of the health of a bore/cylinder.

    If you would, please take a moment to review the Announcements at the top of the Forum, and be sure to provide the Required Info (serial number) when posting. Thanks!


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  3. Member
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    #3
    Sorry, I would provide the serial number but since it was a used boat I was looking at and not my own I didn't know what the serial number was. So what should I be looking for when I ask for a leakdown test?

  4. Member
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    #4
    Quote Originally Posted by MikeBelter View Post
    Sorry, I would provide the serial number but since it was a used boat I was looking at and not my own I didn't know what the serial number was. So what should I be looking for when I ask for a leakdown test?
    all 8 cylinders within a 10% leak down engine still under warranty? or can you add to warranty?
    2022 z519 cup 225 merc 4s ser # 3B210484. 2--hds12 live units. 2 poles, atlas plate, ghost, hamby's, active target, merc digital gauges
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  5. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #5
    10% would be the outside edge. Personally- I wouldn't even consider buying a used engine (expecting to use it for long-term) if the leakdown exceeds 5%.


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
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  6. Member
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    #6
    Quote Originally Posted by EuropeanAM View Post
    10% would be the outside edge. Personally- I wouldn't even consider buying a used engine (expecting to use it for long-term) if the leakdown exceeds 5%.
    Good to know.!!
    Last edited by mactlman; 01-25-2023 at 07:29 PM.
    2022 z519 cup 225 merc 4s ser # 3B210484. 2--hds12 live units. 2 poles, atlas plate, ghost, hamby's, active target, merc digital gauges
    2002 basscat pantera 3 (dad bought new) sold 8-2-22
    2000 stratos 20 ss (bought new) 200 hp Rude ficht great boat/motor sold 11-21
    pulled by a 2500HD Denali
    proud dad of an ARMY Captain
    MAGA
    ASE/GM Master tech before tools

  7. Member
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    #7
    Thank you, that is good to know!