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  1. #1
    Join Date
    Aug 2008
    marietta, ga, usa

    Default Problems with Prestolite trim pump

    I need an exploded parts illustration for an old style Prestolite power trim pump from my 1977, 4 cylinder Mercruiser (4.3l). This is the old style high pressure, low volume (round motor, rectangular reservoir) pump used with the smaller diameter rams. I took it apart to troubleshoot a motor problem (which is fixed) and disassembled the pump to clean it at the same time. When I reassembled the pump and valves, the "down" side wouldn't pump fluid at and then I adjusted the pressure screws and now it pumps fluid in spurts but not much volume. The "up" side works fine and puts out a strong solid stream of fluid so I know the gears are still good. If I run down the adjustment screw any more on the "down" spring, there won't be enough threads left to hold the lock nut. I have Clymer and Seloc manuals but neither give a breakdown of the pump. I have access to a high pressure hydraulic test set but need to get the "down" side pumping first. Any help is appreciated. Thanks, SG

  2. #2
    Join Date
    Aug 2006
    SW Ohio, USA

    Default Re: Problems with Prestolite trim pump

    Not enough fluid in the system, air in it, dirt in the system or worn seals?

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