Welcome Guest - Sign Up today
Welcome Guest - Sign Up today
Store Links Mobile - Shop Now



Help Tip: If you have a question that has not been answered to your satisfaction in the archives, it is always best to start a new thread of your own. By starting your own thread, you will receive the maximum number of views by forum members.

Below are some additional forum policies in hopes of all iboats members will follow, Thank you.

1. Please do not reply to old topics or hijack existing topics. Old topics of a technical nature are like a library book, Please do not write in them.

2. Old topics should be considered archives and used for reference only. Please do not reply to them.

3. Do not take over someone elseís topic (aka hijack) with your own question, even if it is similar. If you have a question that has not been covered to your satisfaction in the archives, it is always best to start a new topic of your own.

4. If you have a question for the original poster (OP) and the topic is over 30 days old, send the OP a PM, he may not even visit the forums any longer, or may not notice your question in the old topic.

5. By starting your own topic, you will receive the maximum number of views by forum helpers that may not even notice your question when itís posted at the end of someone elseís topic. And those answers will be specific to your particular issue.

6. Please do not post to topics that have been inactive for more than 3 months unless you are the original poster. We have very active forums and any topic that remains inactive for that long should be considered "dead". It is especially confusing when there is an entirely new question posted to an old topic.

7. Posting at the end of any topic is considered to be hijacking the original posters topic which in turn subjects the topic to be closed if it continues to happen thus not making it fair to the original poster in the future had for some reason he/she needed to return for additional information or provide an update of the problem solved which is always welcomed within a reasonable amount of time frame.

8. Please note that you should see a red banner pop up near the bottom of each inactive topic asking you not to reply to old topics. The Red banner will read: Please note this topic has been inactive for 90 days. For the best results, please start a new topic.

Thank you all in advance for doing your part in helping iboats run a smooth ship.

Additional forum rules linked below.
See more
See less

1987 Mercruiser Alpha One trim question

  • Filter
  • Time
  • Show
Clear All
new posts

  • 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.