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  1. #1

    Question Sea Water Pump Shaft / Fuel Pump Cam Troubleshooting Question

    I have a 1997 7.4L (454) Mercruiser Bravo carbureted engine with a sea water pump. The shaft inside the sea water pump has an offset cam which activates the mechanical fuel pump lever. There is a steel Slip Ring over the offset cam, which apparently acts as a "bearing" on which the fuel pump lever to ride. I'm trying to troubleshoot this offset cam/ Slip Ring. How much "play"/ "slop" is acceptable for this Slip Ring? I trying to determine if the offset cam on the shaft is worn too badly and needs replacing? I used a magnet and can move the Slip Ring approximately 1/16" to 1/8" perpendicular to the shaft/cam surface. Is this too much "play"/ "slop"? I have a factory service manual but it only shows disassembly/ reassembly. It doesn't have any measurement specifications or troubleshooting details.

    I purchased a new fuel pump because I lost fuel delivery to the carburetor, and the fuel lines and water separator are not clogged. However, the I'm thinking that the culprit could be a worn sea water pump shaft offset cam which isn't properly activating the mechanical fuel pump lever, or a combination of the two factors - bad fuel pump and worn shaft. Before I reassemble the fuel pump/ sea water pump I'm trying to determine if I need go go ahead and rebuild the sea water pump with a new shaft?

  2. #2
    Join Date
    Sep 2008
    Maryland - USA

    Default Re: Sea Water Pump Shaft / Fuel Pump Cam Troubleshooting Question

    Been a while since I had one of those apart....and I can't say i remember any significant radial play in the slip ring....I'd suggest measuring the 'lift' of the fuel pump 'lobe' and that will give you a much better assessment. finding a spec value is a challenge - I've found 3/8" is nominal based on measuring several engines over the years. FWIW, those pumps are not known for long service lives....and they come is one and two piece versions...

  3. #3
    Join Date
    Jun 2008
    Island Heights, NJ,

    Default Re: Sea Water Pump Shaft / Fuel Pump Cam Troubleshooting Question

    Was there proper lube level (Hypoid 90) in the housing??? Is/was this oil undiluted by a fuel leak ??
    Capt Bob
    1969 23ft ChrisCraft Lancer
    Merc 5.7L 260HP/ Volvo 280

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