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TRS trim wiring issue - “black box”?

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TRS trim wiring issue - “black box”?

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Old 06-13-2018, 10:27 PM
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Default TRS trim wiring issue - “black box”?

I ran into problem with my port side trim. While out Sunday, I could not raise the drive with the ignition on. If I turned off the ignition, the trailer circuit wPold allow the drive to come back up. Looking at it today, it appeared to be an issue with the purple with white stripe wire that was supposed to be providing power to the up circuit. I connected the up wire to the same pole as the down side, and it works for now, it it isn’t right.

Lookig at Formula’s wiring diagram, it shows this purple with white stripe wiring going to the “Merc Black Box” which then says see Merc literature. I cannot find this wire at the trim pump. Where does it go? What’s a Merc Black Box?

Anyone?
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Old 06-13-2018, 11:42 PM
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dual trim control box,
pencil pointing at what i think is the wiring schematic for it.
it is part of a harness that plugs into the wiring between the dash and the pumps which also have plugs on them.

no promises but think this is it, have 2 copies of same book no problems dropping 1 in the mail to you

edit in,
i might, maybe have 2 wire harnesses that go from the box to the pumps, believe they are plugged on both ends
will check tomorrow as i have to look for some other stuff as well.


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Old 06-14-2018, 06:33 AM
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Originally Posted by outonsafari View Post
dual trim control box,
pencil pointing at what i think is the wiring schematic for it.
it is part of a harness that plugs into the wiring between the dash and the pumps which also have plugs on them.

no promises but think this is it, have 2 copies of same book no problems dropping 1 in the mail to you

edit in,
i might, maybe have 2 wire harnesses that go from the box to the pumps, believe they are plugged on both ends
will check tomorrow as i have to look for some other stuff as well.

Yes that's exactly what it is. A real pita to figure out. Check your trim limit switches. I don't remember a whole lot about troubleshooting it but I do remember this box depends on them.
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Old 06-14-2018, 08:29 AM
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Originally Posted by outonsafari View Post
dual trim control box,
pencil pointing at what i think is the wiring schematic for it.
it is part of a harness that plugs into the wiring between the dash and the pumps which also have plugs on them.

no promises but think this is it, have 2 copies of same book no problems dropping 1 in the mail to you

edit in,
i might, maybe have 2 wire harnesses that go from the box to the pumps, believe they are plugged on both ends
will check tomorrow as i have to look for some other stuff as well.
I found a copy online of the chapter that covers this. I appreciate the offer! now I just need to figure it out.

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Old 06-14-2018, 08:33 AM
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Originally Posted by Mbam View Post
Yes that's exactly what it is. A real pita to figure out. Check your trim limit switches. I don't remember a whole lot about troubleshooting it but I do remember this box depends on them.
Seems like it.

My boat doesn’t have any trim limit switches to my knowledge. All of my pumps will continue running in either direction; always has.

I tried looking at the harnesses last night, and found some purple wires that were splices together. I’m assuming this was done to close the trim loop, but I can’t be sure.

Is it okay to leave it bypassed? I’d rather have it working, but in my case I don’t think it has ever worked as intended.
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Old 06-14-2018, 01:46 PM
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Purple/white wire is the hot up wire which would go to the trim limit switch. Blue/white wire comes from the limit switch to the pump solenoid. Purple/white and blue/white would be connected together to bypass the limit switch.
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Old 06-14-2018, 02:19 PM
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Originally Posted by picklenjim View Post
Purple/white wire is the hot up wire which would go to the trim limit switch. Blue/white wire comes from the limit switch to the pump solenoid. Purple/white and blue/white would be connected together to bypass the limit switch.
I’ve not yet found a trim limit switch in this boat... where would this be typically? It’s definitely not on the drives.
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Old 06-15-2018, 02:13 AM
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There are 2 round "pucks" on the sides of the gimbal ring where the drive pivits to trim. The one on the port side is the limit switch. The one on the starboard side is the trim sender for the guage. The wire connections would be inside the boat back around the transom. Follow the Blue/white wire from the trim pump solenoid and it should plug together with one of the wires from the limit switch. The other limit switch wire should plug together with the purple/white wire coming from the helm. If the limit switch has been bypassed the purple/white and blue/white wires will be connected together.
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Old 06-15-2018, 06:58 AM
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I should have clarified....

I know where they’re supposed to be. Mine are cut, and look like they’ve always been cut.
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Old 06-15-2018, 07:03 AM
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And yes, there is splicing of purple and blue wires in the harness near the pump (but no purple/white).

Where does the purple/white wire originate from? I’ll need to break out the schematics I guess. It doesn’t appear to come from the helm; it goes into the trim wiring harness.
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