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1986 Mariner Magnum 150hp 6cyl Trim not holding motor up

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  • 1986 Mariner Magnum 150hp 6cyl Trim not holding motor up

    My trim motor will trim up and down the motor. However, when I trim it up, it will eventually loose the pressure and settle back down.

    I have played with the manual trim screw and if I loosen it, it will lower the manual and then tighten it will stop.

    I would like to replace the trim screw but there is a washer on the inside of the housing so that I cannot remove the screw.

    BTW there has never been any fluid that has leaked from the trim motors onto the driveway or in the water.

    Two questions.
    1. How do I remove the retaining washer and it seems to be a full circle washer.
    2. If the screw isnt the problem, then what else might the problem be?

  • #2
    Any thoughts


    • #3
      Here is the Manual for the MID SECTION Power Trim Square Motor And Round Motor Design

      This manual is not for my exact motor but I have to imagine they are very similar. The pictures looks identical.

      From what I can tell, the problems will be as follows

      G. Does not hold trim position under load or
      I. Leaks down and does not hold trim.

      2,5,6 or 2,5,7
      2. Pump assembly faulty.
      5. Manual release valve leaking (check condition of O-Rings) (valve not fully closed).
      6. Lower check valve not seating in port side trim ram
      7. Upper check valve not seating in port side trim ram.

      One other thing I might add is that when I have been in the water for a while and I start to raise the trim, the motor spins for a bit and then it seems to grab and start to raise. Not sure if that is the trim motor building up pressure?

      Click image for larger version

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      • #4


        • #5


          • #6
            Has anyone had to deal with this problem?


            • #7


              • #8
                how interchangeable are the trim parts from other motors? Could I buy an older motor and get the trim parts off of it?


                • #9
                  Manual release valve has been changed. However , that didn't seem to fix the problem.

                  Now what?
                  Change orings on pistons ?


                  • #10
                    Took apart the port trim rod and cleaned it up. The check valve is metal and looks like there isnt much that could go wrong with it. The ram has an oring on it that could probably be changed but I didn't have the kit.

                    Put it back together and tried to prime it and get a gurgling noise. I am not sure if battery is weak or if the motor is shot.

                    Anyone buy from these guys?


                    seems like a good price, problem is it is from china.

                    I think I am going to take the trim motor off and the pump just to clean it up a bit.

                    Looks like there is a Canadian distributor as well.
                    In business for 30 years in eastern Tennessee, we feature the highest quality starters, alternators, generators, and electrical parts for your vehicle, boat, watercraft, motorcycle, ATV, farm tractor, or any application. We are dedicated to offering the lowest prices and the absolute best service, period. Our friendly, knowledgeable staff is ready to assist you with any question you may have, and we will ship your order promptly and efficiently. We are committed to you.
                    Last edited by Coxwain; October 5th, 2017, 10:27 AM.


                    • #11
                      The trim is off the boat now. The motor has been inspected, the armature tests fine, the brush tray is shot. The tray is around $125. So I think I'm going to buy the Chinese motor and pump and give that a try.

                      Problem is that I need the boat for this weekend and I won't have the replacement part by then.

                      Can I use the boat without the power trim installed? Can I manually lock the trim in place like I do on mu 9.9?
                      If so how do I do that?


                      • #12
                        I got lucky and total parts Canada was next day delivery in toronto .

                        I spent the entire day cleaning the trim and installing the new one.

                        Big problem was removing the trim motor from the trim assembly. I had to put a torch to it and it came right out. There are no set screws for this .

                        Install went surprisingly good. The new relays have to be used and here is why.
                        The old pump is 3 wire, ground wire, up wire, down wire. When the solenoid clicks in it lights either the up or down trim to hot and drives the motor

                        The new 2 wire motor works based on reversing the voltage to change direction. So one wire is hot the other is ground and that moves the trim up. Reverse and the ground is now hot and the hot is ground and it reverses the motor the opposite direction. The relays are needed to accommodate that.

                        I left the old solinoids in the motor and disconnected the hot wire to them. .

                        One think on my trim wire from the old harness there was a hot wire there and I disconnected it. I'm not sure if it was being used for something else but I don't think it was needed for the trim? I should check out the wire diagram to see.

                        Anyway, it works now.

                        One thing I should have done was replace all the rings at the same time, but I didn't have the kit or the tools and was in a rush to use on the thanksgiving weekend in Canada.

                        I'm not sure if the bleed down is fixed, but I think after all this trouble, I'll keep it like this.


                        • #13
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                          Another update, bleed down is still present.

                          I think if I was to fix this, here is what would be left to try.
                          1. Oring kit for Ram and 2x trim pistons.
                          if that didnt work.
                          2. Change or clean the check valve in the ram piston.
                          if that doesnt work.
                          3. Change the check valves in the trim pisionts.

                          Either way, I am done going any further with this for this year.