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Primer bulb filling empty carbs: '95 OceanRunner 225 w/OMS

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  • Primer bulb filling empty carbs: '95 OceanRunner 225 w/OMS

    A curious question. The OMS oil mixture system meters oil into the fuel inside the fuel/oil pump. As I understand it, it does this based on the pulses from the crankcase, which drive the air pump.

    If using the primer bulb to pressure up after draining the carbs, how does this mix the fuel with oil, since the motor isn't turning? It seems this would be straight gas going into the carbs. What don't I understand?

  • #2
    Re: Primer bulb filling empty carbs: '95 OceanRunner 225 w/OMS

    Interesting question... one I've never really gave any thought to in the past.

    However, going back in time (1984 to whenever), OMC's instructions in either installing a new engine of a new VRO pertaining to setting up the oil/fuel scenario of the VRO was simply to have the oil hose disconnected from the VRO and pump the oil primer bulb until it was obvious that all air had been purged from it, then to connect it to the VRO and apply pressure to the oil primer bulb one more time only! Then one was to pump the fuel primer bulb until it became hard.

    This makes one wonder if the fuel primer bulb pulses within the VRO cause oil to mix with the fuel... only one way to find the answer to that and that is to run a hose from the output fitting of the VRO into a container and pump away on that fuel primer bulb.

    However, on a new engine or installing a new VRO, it's best to also run a premix in the tank until one knows for sure that the VRO is functioning properly and the break in period has went as it should. After that, should the carburetors ever be completely empty again for any reason (carb rebuild etc)... your question surfaces once more.

    Not an answer to your question I know... but this does get your post back on top once more.
    Our Questions Require Answers... If You Refuse To Answer Our Questions... How Can We Answer Yours?

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    • #3
      Re: Primer bulb filling empty carbs: '95 OceanRunner 225 w/OMS

      Further explanation on my part. This motor had been sitting awhile, so I popped off the brass bowl screws and squeezed the bulb to pressure up and see what comes out. There was bad, discolored gas that ran clear in a few seconds. This tells me that I was pushing straight gas to the carbs, because the air pump in the OMS wasn't turning the oil pump.

      So now I've got carbs full of gas w/o oil. I'm thinking......"this is a good way to damage an engine". Hence, my question. Because the consequences seem obvious, but I don't know the answers.

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      • #4
        Re: Primer bulb filling empty carbs: '95 OceanRunner 225 w/OMS

        This is what I'm going to do. I'm going to fill the water separator with 50:1. Then I'm going to unplug the fuel inlet to the pump and use the primer bulb to fill the line with it. Then I'm going to plug back in, crack the 6 brass screws and flush the carbs with the 50:1. I'll refill the water separator, fog the cylinders, test the no-oil alarm, and then fire it up.

        I think it makes sense. Any flaws?

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        • #5
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          Re: Primer bulb filling empty carbs: '95 OceanRunner 225 w/OMS

          Interesting post. My '98 Johnny 150HPV6 has a vapor seperator with an inlet needle and float. When you "Prime" the motor, straight gasoline fills the vapor seperator and doesn't go beyond it. When you crank the motor the straight gasoline drains into the OMS pump, gets mixed with oil and sent o the carbs. It begs the question as to why you don't have a vapor seperator.

          BTW none of the Mercs with oil injection have vapor seperators either. The oil pump is "teed" into the fuel line. They are sure to get straight gasoline to the carbs, when primed.

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