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Thread: 454 Mag Gen V Fuel Pump Questions

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  1. #1
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    454 Mag Gen V Fuel Pump Questions

    454 Mag Gen V Fuel Pump Questions

    On my 1994 Baja 260CD I have the Fuel Pump mounted to the top of the Raw Water Pump Housing...

    Tonight I took the Fuel Pump off of the Raw Water Pump housing to clean the nipple that connects to the breather hose going to the carb, I noticed there was Raw Fuel inside the Raw Water Pump housing where the Fuel Pump arm rides on the rotating cam, there also appeared to be oil or thicker dark liquid in with the fuel in this area cam area..

    Someone advise me of what is happening...
    My thoughts are maybe the fuel primer is leaking fuel into the lower portion of the housing.
    Wondering why the cam area looked like it had heavy oil in the cavity..

    This is the rocker arm on the bottom of the fuel pump.



    This is the Raw Water Pump that the fuel pump is mounted to, the cavity seen is the area i am talking about.

    Last edited by crisistc; 01-09-2018 at 11:46 PM.

  2. #2
    Baja Supporter JerseyOutlaw's Avatar
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    Re: 454 Mag Gen V Fuel Pump Questions

    Quote Originally Posted by crisistc View Post
    454 Mag Gen V Fuel Pump Questions

    On my 1994 Baja 260CD I have the Fuel Pump mounted to the top of the Raw Water Pump Housing...

    Tonight I took the Fuel Pump off of the Raw Water Pump housing to clean the nipple that connects to the breather hose going to the carb, I noticed there was Raw Fuel inside the Raw Water Pump housing where the Fuel Pump arm rides on the rotating cam, there also appeared to be oil or thicker dark liquid in with the fuel in this area cam area..

    Someone advise me of what is happening...
    My thoughts are maybe the fuel primer is leaking fuel into the lower portion of the housing.
    Wondering why the cam area looked like it had heavy oil in the cavity..

    This is the rocker arm on the bottom of the fuel pump.



    This is the Raw Water Pump that the fuel pump is mounted to, the cavity seen is the area i am talking about.

    The fuel pump uses gear oil for the seapump driven lobe, same as your drive oil. There's a flathead screw on the side of the pump and gear oil should be filled to that height. I had mine apart last year and I had fuel in mine to, I drained it and put fresh oil in. I haven't had a problem. Add checking and changing your fuel pump gear oil to your normal maintenance

    Sent from my SCH-I545 using Tapatalk
    "Fine Whine"

  3. #3
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    Re: 454 Mag Gen V Fuel Pump Questions

    Quote Originally Posted by JerseyOutlaw View Post
    The fuel pump uses gear oil for the seapump driven lobe, same as your drive oil. There's a flathead screw on the side of the pump and gear oil should be filled to that height. I had mine apart last year and I had fuel in mine to, I drained it and put fresh oil in. I haven't had a problem. Add checking and changing your fuel pump gear oil to your normal maintenance

    Sent from my SCH-I545 using Tapatalk

    I wonder why it is getting RAW Fuel past the pump... Surprised that you also had fuel on the other side of yours, mine is from 94 and yours is much newer being an 05, maybe the seal in the diaphragm is worn...

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    Baja Supporter JerseyOutlaw's Avatar
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    Re: 454 Mag Gen V Fuel Pump Questions

    Quote Originally Posted by crisistc View Post
    I wonder why it is getting RAW Fuel past the pump... Surprised that you also had fuel on the other side of yours, mine is from 94 and yours is much newer being an 05, maybe the seal in the diaphragm is worn...
    Yes the fuel does leak past the diaphragm. buy a fuel pump rebuild kit and rebuild the pump... There's a great write-up on here in the how-to section that Smurf wrote up. I repowered the boat in 14', sold the stock power and repowered with a 96' 525.
    "Fine Whine"

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    Baja Supporter tablerocker's Avatar
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    Re: 454 Mag Gen V Fuel Pump Questions

    Wow...I'm surprised Mercruiser is using mechanical pumps.
    My Yamaha 454 has an electric one.
    Table Rock Lake is my home away from home, and big block power rules.

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    Baja Supporter Nailit's Avatar
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    Re: 454 Mag Gen V Fuel Pump Questions

    Quote Originally Posted by tablerocker View Post
    Wow...I'm surprised Mercruiser is using mechanical pumps.
    My Yamaha 454 has an electric one.
    My 98’ 454 mags dont have a mechanical, but has a fuel pump in the cool fuel system that pulls fuel through the filter head from the tank.. hence the vapor lock issue. So that wasnt exactly a good idea either. Though, running return line to fuel tank does help or eliminate when running summer blend non-ethanol.

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    Baja Supporter BigMeaney's Avatar
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    Re: 454 Mag Gen V Fuel Pump Questions

    My 502 had the same set-up and the mechanical pump feeding the electrical pump in the VST tank. The diaphragm in the mechanical pump leaked gas into the gear oil reservoir and when I was running at around 4000rpm it sounded like a bomb went off under my engine hatch. It was the shaft seal from the sea pump blowing out of the housing due to the fuel in the oil. Cost about 700.00 to replace both pumps.

  8. #8
    Baja Supporter tablerocker's Avatar
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    Re: 454 Mag Gen V Fuel Pump Questions

    Quote Originally Posted by BigMeaney View Post
    My 502 had the same set-up and the mechanical pump feeding the electrical pump in the VST tank. The diaphragm in the mechanical pump leaked gas into the gear oil reservoir and when I was running at around 4000rpm it sounded like a bomb went off under my engine hatch. It was the shaft seal from the sea pump blowing out of the housing due to the fuel in the oil. Cost about 700.00 to replace both pumps.

    DAMN!
    I'll bet that was uh...'interesting'...
    Table Rock Lake is my home away from home, and big block power rules.

  9. The Following User Says Thank You to tablerocker For This Useful Post:

    jefflee1988sunsport (01-22-2018)

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