Fogging a 7.4 MPI Merc

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joncrisler

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For my Merc 454 EFI / MPI engine (2000 model year, based on the L29 GM motor)- there is a Schrader valve on the fuel rail- can this be used to inject fogging oil into the engine ? Fogging oil can be obtained with the OMC service valve adapter for EFI outboard engines. Is this Merc/GM valve compatible with the OMC valve ? Would this work ?
 
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joncrisler

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Re: Fogging a 7.4 MPI Merc

Thanks for the info - now that I recall I have seen that before. I dont have that sort of tank, so I was hoping the service port might work.
 
Don S

Don S

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Re: Fogging a 7.4 MPI Merc

Don't overthink it. Get any 1 gallon gas can, doesn't have to be an outboard tank. Get a piece of 3/8" fuel hose from the auto parts store. Unhook the fuel line that goes from the boats gas tank to the engine, from the engine.
Stick your fuel hose into your fogging mixture and hook it to the engine connection. The pump will suck the gas out of the can.
 
zbnutcase

zbnutcase

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Re: Fogging a 7.4 MPI Merc

I use one of the plastic hanging tanks motorcycle shops use to run bikes with the tank off...works great 'nutcase
 
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ulster1

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Re: Fogging a 7.4 MPI Merc

I am going to follow this procedure for my twin 4.3 efi.
After the 5 min of run time do you pull the hose and let the motor stall or just shut it down.
 
Don S

Don S

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Re: Fogging a 7.4 MPI Merc

Did you read the service bulletin I linked to above? The LAST sentence says DO NOT run the system out of fuel.
With a 4.3, you might want to let it run more than 5 minutes. You will never use up all the fuel in the filter in 5 minutes. With a 7.4 yes, but not a 4.3. More like 15 minutes at 12 to 1500 rpm.
 
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joncrisler

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Re: Fogging a 7.4 MPI Merc

zbnutcase said:
I use one of the plastic hanging tanks motorcycle shops use to run bikes with the tank off...works great 'nutcase
Click to expand...

Hey thanks, thats a good idea / alternative. I am going to search around for a used outboard tank to start.
 
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Deepblue22

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Re: Fogging a 7.4 MPI Merc

Is there any chance running oil through the fuel as described would clog up the injectors or foul the plugs ? Is there a springtime procedure to get it going again ? Would it be a good idea to run some kind of automotive type fuel system cleaner or injector cleaner product come springtime ?
 
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fisherman73

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Re: Fogging a 7.4 MPI Merc

Just out of curiousity, why do you need to mix up so much solution ? It seems that it could be accomplished with a fraction of that amount.
 
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