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Bennet trim tab pump-gctid809588

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    Bennet trim tab pump-gctid809588

    Ok guys, I have a '89 3870 with four bennet tabs. I was noticing they all weren't moving. Port side would work and starboard would not work. Mechanic said he switched the hose from port to starboard and then starboard would work and port would not. Said I needed a new pump. Is there another way to check the pump or is it truly a bad pump and replacing it would correct my issue. Thanks for all responses.
    '89 3870 M/Y
    Located on Galveston Bay
    Prior boat '85 300SB Sea Ray
    Lost in Hurricane IKE

    If the pump runs one side it'll run the other. You likely need to replace the solenoid for the side that doesn't work, depending on how corroded things are at the pump sometimes it's just easier to replace the entire pump (HPU) ask me how I know :lol:
    Edmonds, WA
    "THE FIX" '93 2556
    Carbureted 383 Vortec-Bravo II
    The Rebuild Of My 2556
    My Misc. Projects


      Send a message to Tabman. He'll help you troubleshoot the issue:
      1999 3788, Cummins 270 "Freedom"
      2013 Boston Whaler 130 SS
      Anacortes, WA
      Isla Verde, PR


        As suggested If the pump works in both directions, you may have one of two things going on:

        ...... a faulty solenoid valve

        ...... a faulty circuit to that solenoid valve

        Use the tried and proven P of E ( process of elimination).

        Rick E. (aka RicardoMarine) Gresham, Oregon
        2850 Bounty Sedan Flybridge model
        Twin 280 HP 5.7's w/ Closed Cooling
        Volvo Penta DuoProp Drives
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        Please, no PMs. Ask your questions on forum.


          It is definitely either the solenoid or bad connection (or both). Simple test is to press BOTH of the port and starboard switches first in one direction then the other. BOTH tabs should move, indicating pump is OK. Go from there.

          Good luck.
          Retired, computer expert / executive
          Bayliner 285 Cruiser / Mercruiser QSD 4.2L 320 HP Diesel
          Live in the Bay Area, CA, USA, boat in Turkey
          D-Marin @ Turgutreis in Bodrum/Turkey
          [email protected]
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            Better yet, convert to electric trim tabs and get rid of the pump altogether. Nothing to leak anymore. They make a conversion kit for Bennett hydraulic to electric and you keep the same tabs. Very easy to do and less parts in the end. They also won't leak down and change position. One of the things I did to my last boat and is on the list for my current boat.
            1995 2859 -extensively rebuilt/restored 2016/17
            496 big block - Bravo ll leg
            The Doghouse
            Prince George BC


              Probably not the whole pump.

              Check out this video

              Then do step 3 below and let me know what you find.

              Tom McGow

              Bennett Marine

              Fluid: Automatic Transmission Fluid (ATF) any type. Hydraulic Power Unit is self bleeding, running the Trim Tabs up and down 3-4 times will purge air from the system.

              Fuse: 12 volt system use 20 amp in-line fuse on positive. (24v & 32v use proportionately smaller)

              Red= Port Valve

              Green= Starboard Valve

              Blue=Motor Forward (pump pressure)

              Yellow= Motor Reverse (pump retract)

              Black on HPU=Ground

              Orange on Helm=Control Positive


              1.If one side is not operating reverse hydraulic lines on the front of the Hydraulic Power Unit to determine if the malfunction is in HPU or actuator / hydraulic lines. If after reversing the lines symptom shifts to the other side the malfunction may exist in HPU. If the symptom remains on the same side, malfunction may exist with the actuator / hydraulic lines

              2. Is the unit receiving a solid 12 volts? Low voltage will some times cause the solenoids to not open preventing the tabs from moving even though the pump motor is running.

              3. Conduct the following test:

              Remove the wires from the helm control and touch together as follows:


              Orange (+), blue, red= Port trim tab down

              Orange (+), blue, green=Starboard trim tab down

              Orange (+), blue, red, green= Both trim tabs down

              Orange (+), yellow, red= Port trim tab up

              Orange (+), yellow, green=Starboard trim tab up

              Orange (+), yellow, red, green= Both trim tabs up

              If the trim tabs function correctly for each wire grouping then the switch is at fault. Also note that any loose or missing screws on the back of the switch (whether a wire is connected there or not) can cause the pump to malfunction.

              This test may also be done right at the pump by substituting a "hot lead" for orange. There is usually a connector to the wire harness within a foot or so of the pump. You want to check this connection for corrosion. You may wish to cut the connector off on the pump side and try the test on bare wires.

              4. If you suspect corrosion on the wire connector near the pump, cut it out, test as above and reconnect using butt splices.

              5. If you conclude the problem is in the pump, contact me. Bennett Trim Tab Systems carry a five year warranty.

              6. Check to see if there is a relay in line on the wiring harness near the hydraulic power unit. If there is it is an Interrupter Relay (IR1000). It prevents the system fuse from blowing if you try to actuate one trim tab up and the other down at the same time. After you test as outlined above, try removing the relay from the wiring harness and retest the unit.(Note: the interrupter relay is no longer used in current Bennett Trim Tab systems and has been replaced with a Switches that "lock out" preventing a blown fuse).
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