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  1. #1
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    1984 Mariner 75 Compression

    There is a 1984 Mariner 75hp I am getting ready to sell, that I think it is in great shape and it runs good. I went to do a compression check on it and the numbers all came up consistently between 175-185lbs. I considered this excellent, but now I'm wondering if this is too high. I did forget to open up the carbs when I tested, but I doubt that would make it go higher as opposed to lower. I'll try the test again, but does this sound normal?

    The motor is 2/3's of a Tower of Power, it just has the 4 cylinders inline.

  2. #2
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    try another compression gauge..
    Checkmate 2002 Convincor 270 496 MAG-HO

    2003 Cougar 22MTR w/300xs SOLD
    90 21Skater w/300xs - sold
    98 STV Euroski w/280 - sold


    2006 Trailblazer SS 6.0l 395hp

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  4. #3
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    Did you fog it up real good, if so run it clean and try again.
    Maybe at some point someone slipped high domes in it too?
    Last edited by FMP; 11-23-2020 at 10:55 AM.

  5. #4
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    So I did try another compression gauge. That was a good idea, but the results was similar, so that is not the problem.

    ... and to answer the question about fogging, yes it had been fogged a while back for storage, and I sprayed a bit more just before testing because I worry about spinning a dry engine for fear of causing damage. This last time though after I spun it several times and cleared some of that oil out I started to get readings closer to 150. So I believe if I actually ran the engine first and then did a test I suspect it would show something more normal as mentioned.

    Thanks for the tips guys.

  6. #5
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    So you still have room for the high domes

  7. Likes Glastron1987 liked this post

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