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Trouble Shooting Trim Tabs

fishy talesfishy tales Posts: 56 Greenhorn
edited June 3 in Boating #1
What to check or do now?

I noticed one tab on the starboard side seemed to be a little off canter and affecting the boats ride. I did some checking for some of the normal causes: checked for corroded/ broken wires, fluid amount and even reversed the lines to try and pin point it down. When i reversed the lines, the starboard tab worked fine and the port side didn't, so that tells me there is something in the HPU that may cause this problem. When working the HPU from the switches i can hear it trying to work. With the switches the port side seems to be louder then the starboard side. I read where there are solenoids for each, but not able to determine if it is bad or not.

Is there anything i can try or check with out just replacing parts?

Any and all imformation one can provide me is greatly appreciated.

:Rockon Maybe - Maybe Not --- Lets Find Out :Rockon


  • TabmanTabman Posts: 146 Deckhand
    Fishy Tales,

    Can you tell me what type of boat you have and how old the Trim Tab system is?

    If the starboard Trim Tab is not moving and you can hear the pump running than the solenoid valve is not opening. It is really easy to troubleshoot.

    Here is a link to a video that covers how the system works and basic troubleshooting
    And here is a link to a video that covers One Tab Operates, Other Does Not

    Below you will find troubleshooting that you can print and take to the boat. Doing step 3 will allow you to isolate the problem. Pay particular attention to the green wire since it controls the solenoid valve for the starboard Trim Tab.

    Once you have done step 3 let me know what you find and I will be delighted to help.

    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).
  • fishy talesfishy tales Posts: 56 Greenhorn
    I have a Proline 26Sport 2002. I would imagine the system is that old as well since the tabs are molded into the hull of the boat. I had replaced the rocker switch about 6 months ago and all has been fine till this past weekend, after work tomorrow i will perform the wiring test just to be sure.

    thanks for your help
    :Rockon Maybe - Maybe Not --- Lets Find Out :Rockon
  • TabmanTabman Posts: 146 Deckhand
    Make sure that none of the screws on the back of the rocker have come loose, even if they don't have a wire attached that can cause your problem.

    Bennett Marine
  • fishy talesfishy tales Posts: 56 Greenhorn
    Test Conclusion:

    I took the switch apart and tested the wires as described in note #3, everything seemed to work except for the green wire which activates the starboard solenoid. I put the switch back together making sure all wires were tight and secure as well as with the one screw with no wire connected to it. Went to the connector at the HPU and disconnected it, ran a 12v jumper wire and tested each one of the prongs on the connector. Each one seem to activate something whether it was the pump or solenoid EXCEPT the green wire again, no clicking of the solenoid.

    So knowing this now, it is safe to say that the solenoid for the Starboard side is bad?

    Appreciate your help in trouble shooting this matter.
    :Rockon Maybe - Maybe Not --- Lets Find Out :Rockon
  • TabmanTabman Posts: 146 Deckhand
    Fishy Tales.

    Yes it sounds like the solenoid has failed.

    Check your private messages, I have a solution for you.

    Bennett Marine
  • fishy talesfishy tales Posts: 56 Greenhorn

    Appreciate your help in pin-pointing the problem, and with a solution.


    Fishy Tales
    :Rockon Maybe - Maybe Not --- Lets Find Out :Rockon
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