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Thread: Compression ?

  1. #1
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    Compression ?

    Ok, I have a 01 sea doo rx di ski. This is just the second season I've owned it. It ran give last year. I just started it up for this season and did a compression test on it. One came up with 120, the other came up with 115, both slightly falling. This could be from just not a tight enough seal on the compression tester. What are everyone's thoughts about these numbers? I'm thinking about just running it this season as is and in the fall just start to tear the top end down and rebuild the top end as my winter project...

  2. #2
    I dream skis j-wadd's Avatar
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    Re: Compression ?

    You would like to see the two numbers closer to each other. Make sure you have the compression checker on right and do it with the throttle open

  3. #3
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    Re: Compression ?

    I did it with the throttle open and it came up pretty much the same.

  4. #4
    I dream skis j-wadd's Avatar
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    Re: Compression ?

    That sounds better cool. I am no expert just repeated what I have read here.

  5. #5
    resident guru hafweigthr's Avatar
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    Re: Compression ?

    A good 951 is 130-135 and cylinder to cylinder should be no more than 10% different cylinder to cylinder which is pushing it IMO. By the end of the season you could make things significantly worse running with low compression because eventually the carbon buildup from less efficient combustion will start locking your rings in the piston grooves.

    Now you may get another good year or 2 out of new rings and a hone depending on what the damage is.

    All compression testers are not created equal(calibrated) so you need to know if 120 truly is 120 or not. Testing on a new rebuild (done properly) or against a known good gauge is one way to verify.
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  6. #6
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    Re: Compression ?

    Well I did a compression test on my speedster jet boat in them came back 150

  7. #7
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    Re: Compression ?

    787/717 will have 150-155 psi. The 951 is a lower compression engine. They will typically run all the way down to about 105 though.

    The #s will likely increase slightly after you run the engine for a bit and get things lubed up. I'd just run it for the summer and if #'s drop at the end of the year plan fir a rebuild over winter.

    When the time comes i would revommend a full rebuild on thr 951 and not judt top end.

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  8. #8
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    Re: Compression ?

    Ok how difficult of a job is it to do a complete rebuild?

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