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Mercury 225 HP missing & erratic

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  • Mercury 225 HP missing & erratic

    Just purchased a 1997 225 HP 3 litre mercury on ebay with only said 130 hours run time. Seller said motor ran good before repowering his boat with a EFI model from this carb. motor. This motor's lower unit had been canibalized to a friends motor. This motor was sold without lower unit. I purchased one and attached to motor and tried to run it.
    Motor did not even fire. found that crank position sensor was .250 in. from flywheel. I adjusted to .040. Motor ran but misfired with loud poping sounds
    Sound like it was running only 2- 4 cylinders. ran with erratic idling rpms. After 15-20 minutes it sounded like it started firing on more cylinders (maybe all) and was much quieter with no popping. It ran this way for about 2-3 minutes and then went back to the original pattern. I stopped motor and restarted, and the same thing happened. Starts right away. Smooth running at first then erratic. I openned the carbs just a bit from idle, it starts erratic firing. Any ideas on what to check. Maybe I have missed something on hookup. Compression checked out @ 100-110 PSI. I got fuel, and all plugs are getting spark. Must be problems in timing or something like that. HELP

  • #2
    It may be lean popping which would mean the carbs need to be cleaned.
    Regards
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