Throttle to tach wiring question

Radarcontact

Cadet
Joined
Sep 23, 2011
Messages
26
Hi,
Need to hook up some used gauges, none came with any wiring.

Have a 1986 90hp 6-cyl Mercury outboard motor with power tilt and trim.

Included is a pic of the wires and female pigtail available to me.

NEED to hook up a tach, but also have a speedo, gas gauge and volt meter to wire up.

Speedo I don’t really care about, I’ve got WAZE on my phone if I need to know my speed for some reason. The others would be nice to have (even though I have another volt meter already installed as part of a switch panel, maybe I’ll do the tilt/trim gauge instead).

QUESTION:
When researching this subject I found lots of references to the pigtail and brown auxiliary wire(s). However mine has four wires besides the pigtail. See pic.

They are old and faded, but appear to be
- light (?) blue w/white stripe
- light (?) green w/white stripe
- RED or pink (plugged)
- TAN or brown (plugged)

I think the blue and green go to the trim, but I don’t know much, and the trim already works. Also, the trim gauge just has the familiar S, I, and GND markings.

Would anyone be kind enough to identify these for me? And do I need the pigtail to hook up the tach? *I’m assuming “yes”

Thank you!
// Radar //
 

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Radarcontact

Cadet
Joined
Sep 23, 2011
Messages
26
That end is the control box end. We need to see the cables on the other end of the harness.

Gauge markings - I=Ignition (switched power, usually purple), GND=ground, black, S=sender.

Here's the list of BIA colours.

https://www.cpperformance.com/t-boat_wiring_colors.aspx

Chris......

Hi Chris, thanks. I don’t have the harness; I guess what I was wondering was if I needed it (a new harness #86396A8) to hook up my tach. I’m assuming so and will just go ahead and buy one. Didn’t know what those other wires (bl/wh , gr/wh) were.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,241
Blue/white and green/white are very likely power trim up and power trim down.

Light brown wire is usually the temperature overheat alarm. You might check the color of the wire at the overheat sender, if you have one.

The pink wire???
 
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