Wiring Mess!!a

[SHickey]

Hello and Happy Fathers Day,

I am working on a project, 1974 21' Mirrocraft that has a Mercruiser 140 3.0 motor with a MC-1 outdrive. This boat is in the process of being gutted out considering there are decking screws, red plastic tape, and different colored wires connected together for the same device. It is almost comical how this boat was maintained or fixed and it is no wonder most all of the electrical items; nav lights, instruments, blower, horn, wiper and bilge pump don't work.

I also discovered the forward wiring harness that plugs into the motor wiring harness do not have the same colored wires. This may be due to someone switching wiring harness at one time or another. This mismatch in wire colors compound the problem of trying to figure out what wire goes where when I hook up the ignition, instruments and the neut cut off switch.

At the motor end the female connector has 3 heavy wires; Red/White, Black and Red and 6 thin wires, Green, Brown, White, Purple, Orange and Yellow.

The forward wire bundle with the male connector has 3 heavy wires; Red, Orange, and Black and 6 thin wires White, Tan, Grey, Blue and two Purple wires.

It is very difficult for me to figure out what goes to what considering the actual wire path is hidden by the heavy rubber connector housing.

If anyone could help me figure out which colored wire goes to the different instruments (temp, Volt, pressure, Trim), ignition, and neu cut off connections that would be most helpful. I do not want to just hook things up and experiment if someone may have an old wiring diagram that may match this particular wiring harness I have on this old tin can.

As always, any help is most welcome!!

 

[Bt Doctur]

 

[Bt Doctur]

 

[Bt Doctur]

 

[achris]

You appear to have an early model engine harness and a later model instrument harness.

Engine harness colour to device.

Pin 4 - Red/White (heavy wire) - Alternator output (goes directly to Ammeter)
Pin 1 - Black (heavy wire) - Ground
Pin 6 - Red (heavy wire) - Instrument power feed (also goes to Ammeter, but other terminal)
Pin 3 - Green - Water temp sender
Pin 2 - Brown - Tacho feed
Pin 5 - White - Coil power (ignition ON)
Pin 10 - Purple - Unused
Pin 8 - Orange - Oil pressure sender
Pin 7 - Yellow - Starter solenoid.

Some of the instrument colours don't match any of the Merc instrument wiring diagrams, so may be a mix of wires someone just had laying around at the time. Those you may need to be checked at the instruments themselves.

Sorry, that's the best I can do at the moment.

Chris.....

 

[SHickey]

Thank you both for your responses.

I can see the appropriate color wires leading to the connector but the instrument bundle that gets connected has similar gauged wires but different color wires coming from the instrument bundle.

At the motor end the female connector has 3 heavy wires; Red/White, Black and Red and 6 thin wires, Green, Brown, White, Purple, Orange and Yellow.

The instrument wire bundle with the male connector has 3 heavy wires; Red, Orange, and Black and 6 thin wires White, Tan, Grey, Blue and two Purple wires.

It is very difficult for me to figure out what goes to what considering the actual wire path is hidden by the heavy rubber connector housing.

Are there any older instrument wiring diagrams that may have a wire combination that matches the instrument bundle that I have?

Again, any help goes a long way for me