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1987 Mercruiser Alpha One trim question

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  • 1987 Mercruiser Alpha One trim question

    OK, finally got all my wiring sqared away after hull and interior work. The outdrive has remained in the "up" position since I bought the boat about 5 weeks ago and am presuming it has been in that position since at least 2003 based on last registration. Have a new battery. Trim system will operate "up" and motor will stop running (I am assuming the limit switch is working), the pump motor will not operate for a "down" command. I do not hear the solenoid engage. I plan to clean/burnish all of the connections at the pump and solenoids. Any additional information is greatly appreciated.


  • #2
    Re: 1987 Mercruiser Alpha One trim question

    Take a remote starter switch or heavy jumper wire and jump the 2 1/4 in studs on the down solenoid, the one with the green motor wire attached. If goes down, you have bad switch or solenoid.
    You meet the nicest people at the American Legion.
    "maintenance is always cheaper than neglect"
    "certain parts are USCG approved for a REASON"
    "just because it's in the factory service manual, doesn't mean it's correct"


    • #3
      Re: 1987 Mercruiser Alpha One trim question

      Here is a link to the service manual for your outdrive.




      1969 StarCraft Chieftain, 4.3 Mercruiser Alpha One Gen II

      Link To Restoration Page


      Its What I Don't Say You Should Be Worried About...


      • #4
        Re: 1987 Mercruiser Alpha One trim question

        Thanks guys. I burnished all of the contacts. I took out the relays and tested them on the bench, the down relay has some very high resistance when latched, and does not get any better after exercising it. The up relay is better, but I am going to change it anyway. This should solve my switching issue. I managed to get the drive lowered by applying power directly to the motor. This took some time, the motor would run for a couple of seconds, then stop. I would remove the 12V from the motor lead, wait a few seconds, re-apply 12V, and again the motor would run for a couple of seconds then stop. After about 12-15 times of this, the outdrive was finally lowered completely. I am not sure if there is an overload circuit built into the pump motor that will open when excessive current is being drawn by the motor, any suggestions? I plan on accessing the internals of the pump motor and look for anything obvious. The hydraulic fluid is clean and to the proper level. no issues there. I know there is more than one issue now with the trim system, I will just bite off one piece at a time! Any suggestions are appreciated.



        • #5
          Sign up today
          Re: 1987 Mercruiser Alpha One trim = FIXED

          Thanks for the contributions to my trim issue. Good stuff on the forum to glean information from. I removed the trim motor and solenoid relays, cleaned and burnished all connections. Found that both relays had high resistance when latched when tested on the bench. I was able to disassemble both relays and clean/burnish the contacts (I'm a cheap SOB!, saved $40.00), they work great now. I removed the motor armature and brushes, burnished the armature and cleaned the housing. The brushes were in good shape, no issues. Easy to do, a little time consuming though. I lubricated shaft bushings and re-assembled the motor, tested on the bench, nice and smooth with good torque. These early motors are built very stout! It is fair to say they are much better quality than what you can buy new today. No plastic to get brittle and break. I was fortunate, the pump has nice clean fluid with no need to top off. I did replace the o-ring (packing) between the pump and motor assy's when going back together.

          After re-assembly, turned on the master power and got nice linear up/down trim actuation from the thottle trim switch with good indication on the indicator and correct trim up operation with the skeg stopping at the right height before cavitation can occur. The trailer tilt operation worked correctly for up actuation, but did not work in down. Found the down wire from the switch was disconnected. The previous owner had worked on the wiring at some point and really FUBAR'ed the trim/tilt wiring at the instrument panel. I believe he tried to bypass the bad relay issue with no success and left it that way. I cleaned up his rat's nest and now have proper tilt/trim operation!

          It ended up being four different issues:


          Thanks for your help with the diagrams.