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Oil leak out propellar - unburnt 2 stroke but running smooth?

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  • Oil leak out propellar - unburnt 2 stroke but running smooth?

    Hi all,

    On my 2000 oceanpro 130hp-

    So I recently changed gear oil so was concerned to see an oil patch (thick dark oil trickle not residue) out the propellar exhaust after running on muffs.
    I'm almost certain it's not gear oil, it's black and not smelly. The motor is running sweet from cold, not smoking excessively etc, so it seems odd that excessive 2 stroke oil might be coming through, surely it would run rough?

    Any thoughts? Each time I run for a few mins there is a good 50ml at least dripping out!

    If it's a gas restriction or air leak, again wouldn't it run rough? No alarms, automatic choke drops rpm back when warm etc.

  • #2


    • #3
      It is the nature of your motor running on muffs.-----On a PERFECTLY tuned motor like yours there is fuel and oil pumped through the motor.----This fuel / oil is lost without being used / or compressed and burned to produce power.----Difficult for some to understand I believe.


      • #4
        Hi all , thanks for the replies, just odd that I never noticed this after 5 years of owning the boat. That said, motor is normally trimmed up enough so it wouldn't drip out by the propeller. Just to confirm, this is not residue but as thick as the oil goes in- presumably gas has long evaporated!

        Certainly no leaks under the hood, can a vro leak in such a way that it would continue to seep through long after shutting off as it appears to?



        • #5
          On a carbed 2 strk you do not have complete combustion. That means some fuel oil mix is pushed out of the cylinder and goes out with the exhaust. When the engine gets up to operating temps combustion becomes more complete, and less fuel oil mix is exhausted. It is worse when you run on muffs because there is no exhaust back pressure, and the motor never reaches operating temp.


          • #6
            Had the same issue, thanks for putting my mind at ease. Not experienced it with other outboards but then this one has been purely running on muffs while I sort out my overheating problem (waterways caked with salt buildup and worn water pump)


            • #7
              Had pretty good flushing success with salt away when running in salt water. The converging ring on the prop hub will help draw away some of the unburned fuel that might otherwise stay in the hub and drip on your driveway. You can buy a replacement if yours is missing.


              • #8
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                I have the same problem with my kicker motor when the lake water is cold. The warmer the water is, the better the motor heats up to operating temperature, and the less oil dripping beneath my motor in a full down position.