TOPIC: Mercury Wiring & related color codes

Mercury used a variety of different color codes during the '50s-early '80s, and a variety of different ignition switch set-ups due to a variety of different ignitions used.
So be sure and share what model your Merc is, what serial number it is, and if possible,...Snap a picture or two of the ignition components on the engine, so someone can correctly identify what you have.
Also let us know what color the wires are, both inside the engine cowlings, and in the external harness that attach to the helm area ignition switch.
IF the ignition switch is inside a control box, and unless you are comfortable with the disassembly of the control box, post for help and someone will help you test & identify which hole in the harness plug does what function so that you won't need to tinker with the inside mysteries of the control boxes.
So many ignition components that are getting scarce and expensive are ruined simply because a few questions weren't asked before exploring & assuming.
Doc Frankenmerc

How true.

So just post that info to this thread? I have 2 65 1000s and a 68 1000. The 68 is original AFAIK but not sure of the twins. Id be glad to post that this weekend.

Redden marine supply has every color /guage wire you might need marine grade by the foot

dlatshaw asked, "So just post that info to this thread? I have 2 65 1000s and a 68 1000. The 68 is original AFAIK but not sure of the twins."
Yes,...That way when someone is looking for a wiring clarification they don't need to remember that it was covered under a compression related post.

This is one seriously long ‘write-up’ completed with the intent to assist and send home the importance of being VERY CAUTIOUS when working on the wiring in these classic Mercs.

AND,…I’ll bet that I may have made an error or omission or two in this write-up, so please wait for it to be reviewed for a few days by some of the forum’s Masters as I have been ‘spanked’ before.

Here we go!!!

Be sure and either carefully identify what color wire goes where from the internal harness plug to each specific component, or snap a few clear pixs.
Unless you have the control box open (which can be a 'Pandora's Box for a first timer for sure),…

1) Disconnect the external harness plug-in from the engine,

2) Connect the battery to the large red (+) battery cable and the large black (-) battery cable. If the battery cables are both black, do a continuity test between each of the two large pin holes to each black battery cable. The top large pin hole is positive (+), the bottom large pin hole is (-)
Remember to be holding the external plug in a proper position so that you are definitely looking at it correctly & not upside down while identifying the (+) & (-) large pin holes in the plug-in.

DANGER: The small wire colors can really throw a wrench into things if connected to the wrong place.
Example,...a small 12vdc (+) wire can be red, black, green, purple, or white depending on which harness you are using.

3) Once you have the battery connected,
But not plugged into the motor,
And with the key still 'OFF':
Test for 12vdc by holding your black (-) test lead to the bottom large pin hole and the red (+) test lead to the top large pin hole. You should see a 12vdc reading.
Leaving the black test lead in the (-) large pin hole,...Test each small pin hole with the red test lead for 12vdc. There should not be any small pin holes that show a 12vdc+ result.

4) Disconnect the Battery leads.

5) Now switch your meter to do an OHMS test.

6) With the black test lead still in the bottom large (-) pin hole,
And the ignition switch in the ‘OFF’ position,
Touch the red test lead to each of the small pin holes.
You may find one small pin hole that has continuity – or – you might NOT find one small pin hole that shows continuity.

7) Now,…ONLY if you had continuity between one small pin hole and the bottom large pin hole:
Turn the ignition key to "ON" with your test leads still connected to the same pins and the continuity should vanish.
Do NOT do Step #7 if you did not have continuity in Step #6.
Note: If you have continuity in Step #7,..This would be the circuit to 'kill' the motor's ignition on the magneto, Lightening Energizer, and Alternator Driven Ignitions (adi).
The ‘KILL’ wire color could be either Salmon, White, Orange, Blue, or Black with a yellow stripe.
Other ignition styles may not have this 'kill' circuit used in the ignition so your original plug-in harness may not have a small pin hole that has a small hole with no brass contact or wire molded into the plug-in.

8) Disconnect your test leads and turn your meter back to test 12vdc.

9) Connect the (+) & (-) battery cables to the battery.

10) Turn the ignition key to "ON"

11) In the following tests of the small pin holes,…Do NOT test the small pin hole that had continuity with the ignition ‘OFF’.

12) Hold the black test lead in the large (-) pin hole, and, with the exception noted in Step #11,… test each of the other small pin holes for 12vdc.
There should be (1) small pin hole with 12vdc.
There ‘could’ be (2) small pin holes with 12vdc when testing a DR or early 12vdc dual coil-dual point ignitions.

13) Turn the ignition key ‘OFF’ and the pin or pins that had 12vdc when the key was ‘ON’ should no longer have 12vdc when tested.
This test will identify which pin hole will align with the internal harness’s pin that gives 12vdc to activate the types of ignition that require 12vdc to run, and will shut down the ignition when the key is turned ‘OFF’.
Typically the wire color inside the motor housing for this function will be either Green, Black, White, or Purple depending on which color code is present.
Magnetos, Lightening Energizer solid state magnetos, & ADI (Alternator Driven Ignitions) do not require a pin with 12vdc when the key is ‘ON’.
Magnetos, LEs, & ADIs do however require that the ignition switch being used has the capability to transfer 12vdc internally to different terminals on the ignition switch in the control box so that when the CHOKE is activated or the starter solenoid is engaged,…12vdc is present for those functions.

14) Turn the key to ‘ON’ and hold the choke button ‘ON’. The choke with either be ON by pushing a button down or by pushing the ignition key inward.

15) Hold the black test lead in the large (-) pin hole, and, with the exceptions of the small pins noted in Step #1, Step #12, & Step #13,… test each of the other small pin holes for 12vdc. (1) small pin hole should now have 12vdc. Let go of the choke and the 12vdc should go away.
Now you can identify which pin in the internal harness aligns with this, the CHOKE small pin hole, and determine which color wire inside the motor housing is for the CHOKE.
Commonly the CHOKE wire will either be BLUE or GRAY or YELLOW with a Black stripe.

!6) Turn the key to ‘START’ and hold it there while locating the small pin hole that now has 12vdc.
Remember, do not re-test other small pin holes at this time – only the small pin holes that have yet to be tested. (1) small pin hole will now have 12vdc.
Let go of the START position and the ignition key should spring back to the RUN position, and there should no longer be 12vdc present at the small pin hole identified as the solenoid pin hole.
The wire colors for the solenoid function inside the motor housing should either be YELLOW or YELLOW with a red stripe.

So-o-o-o,…With all these ‘Factory’ variations of wire colors, added with the rainbow of colors that could have been added or switched or spliced over the years by a Technician or a Back Yard Wonder, I hope the reader can see how important it is to positively identify exactly what each wire is doing before attaching it to a component.
Take the time to post a few pictures, or draw wire diagrams of what color wires are being used & ideally what pin is related, and post for help. Patience awaiting assistance could result is saving yourself a TON of money & headaches.

Doc Frankenmerc

Doc,

I am looking to swap motors for next season. The boat has a 1964 mercury 50HP and over the winter I am working on a 1966 mercury 650. Can I use the same external wiring harness and control? I know I will have to change the throttle and shift cable as the motor end is not the same. Can I just plug in the external plug that worked on the 1964 50 HP into the 1966 65HP?

yes you can. the ends are the same just take the pins out of the old ones.if you dont want the oins send them to me.1 914 310 7086 for ?????'s

Granted,...I haven't had my morning coffee yet,...BUT when I read DaveB's post: "yes you can. the ends are the same just take the pins out of the old ones.",...I pictured a mad dentist armed with a pair of pliers pulling the pins out of the internal harness's plug-in receptor.
BUT slowly the fog cleared and I realized Daveb was referring to the ends of the control cables that push & 1/4 turn to hold the aft ends of the control cables to the outside of the engine pan.

Don't remove the black parts - just the stainless pin, spring, & the small spread pin.

And,...Yes you can simply plug in the external harness from the '64 500 to the '66 650 as they both have a magneto that uses the same style magneto kill to shut down the beasts.
I gotsta go get some coffee. I was up 'til 3am, and running slightly late today.

Thank you both for the response. I was VERY confused for awhile there. Like Doc, I was thinking that I was going to be pulling pins out of the wiring harness connector. I am a novice with this stuff and thought, oh man I do not think I want to be doing that.

Dave was talking about the cable connector. Now I understand. So this is even better news. I can use the same control cables also correct? I just remove the small spread pin and the spring and larger pin will come off, leaving only the black section with a hole. That will be the same connection to both my motor throttle and shifter?

So it looks like I can use both the wiring harness and control cables (with minor modifications). That is great.

yes that is correct. if you dont want the pins call me.1 914 310 7086. i can use them.

Dave, I will be keeping the pins until I complete the conversion to the 650 and no longer need the 1964 500. With the same control system, I could easily swap back to the 500 if needed. At some point I will be looking to find a new home for the 500.

While I have your ear, will I need to make new transome holes on the boat? I know the 650 is a bigger motor, but is the connection to the boat the same spaced holes? I did a rough measure of the holes from the 500 and it was close, but I was not in a position to take exact measurements.

cant remember depends on the year.put it on and see. to repair the holes just take a wooden dowl coat it with silicone and hammer it in and cut flush or a little shorter then fill with sealer inside and out. . if you need the holes again just hammer them out.keep my # if you need help.

im looking for some wiring help on my 115 mariner im starting on.. its a 79 and all the wires are breaking off under the cowling.... need to find out their location and repair before i get deep into it. ser. number is 5430550

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