Thread: WOT stutter

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  1. 06-24-2019, 11:55 AM #1
    Mike Z
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    WOT stutter

    This is not a warranty issue (I was told) but a rigging issue. I have a 520L Ranger with a 250 ProXS 2 stroke that developed a WOT stutter (above 5500). Took to the shop and they ran all the tests on it and found nothing wrong. The did however change the fuel line from the bulb to the seperator. Seems Mercury makes a generic splice to make rigging easier. That splice seems to be the reason for the stutter. I now have a solid line and no stutter according to them. I haven't driven it myself but I know others have had this problem and thought Id share.

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    Last edited by Mike Z; 07-03-2019 at 08:58 AM.
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  2. EuropeanAM
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    #2 06-24-2019, 06:40 PM
    Please take a moment to review the Announcements at the top of the Forum, and provide the Required Info when posting. Thanks!

    Be sure to update after you've had a chance to run it. Good idea to get rid of the extra connection, if for no reasons other than eliminating a potential leak and restriction point.
    Last edited by EuropeanAM; 06-25-2019 at 11:24 AM.


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  3. Savage
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    #3 06-24-2019, 08:23 PM
    The extra splice is not likely to cause a problem......thousands of motors rigged like this.


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  4. Mike Z
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    #4 07-02-2019, 09:14 PM
    Quote Originally Posted by Savage View Post
    The extra splice is not likely to cause a problem......thousands of motors rigged like this.
    It appears you're right. RPMs came up but still have a stutter. Talked to the mechanic and thinks air is getting into the system. Back to the shop
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  5. Savage
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    #5 07-03-2019, 06:18 AM
    Air and fuel pressures need tested, along with spark, as the problem is occurring.


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  6. Mike Z
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    #6 07-03-2019, 08:55 AM
    They done both while running and didn't find anything. I had new plugs put in since they pulled them for compression and they had 70 hrs on them.
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  7. EuropeanAM
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    #7 07-03-2019, 10:45 AM
    Sounds crazy but it might be worth dropping the gearcase and taking a careful look up inside the exhaust (as well as down inside the exhaust cavity of the gearcase). Watch for any unusual "edges" of castings.


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  8. Mike Z
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    #8 08-01-2019, 04:16 PM
    Just an update, got boat back in shop with same problem. Mechanic was thinking air in fuel from the boat side. I was there this morning and we ran the boat on test tank, same problem. It was decided to call mercury and ask for guidance. I had to stop by this afternoon and was told mercury is leaning toward a weak air compressor. It don’t show up unless it’s WOT. He had lots of pressures wrote down but I had no idea what they meant.
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