Internal Wiring Harness

[Rip n Lips]

I got the new wiring harness in the mail today and gave my best shot at hooking it all up. I managed to connect everything but a few wires that were not color coded on the old harness. I have an Orange wire (Kill circuit for ADI- not used, tape off) according to CDI instructions...I also have a white wire (12V from key-switch) and 1 jumper wire which is red (connect between recitifier + post and the red terminal on the switch box). The brown wire (tach signal) was the only wire that I could clearly make out on the old harness so that is the only wire from the new harness that I attatched to the switch box. The 2 terminals below the brown wire are empty. I know the directions are correct, but I don't know which terminal on the switch box to connect which wire to. If I tape off the oarnge wire like the instructions say, that means 1 of the 2 terminals would be empty. That can't be right because they all had a wire to them originally...Can anyone tell me what color wire to attatch to what terminal on my switch box or possibly know a site that will show me what each terminal on the switch box is used for? The part number of the switch box is 332-2986. Thanks - Jerry

 

[Chris1956]

Re: Internal Wiring Harness

Jerry, It would help f you told us the year and model of your motor. It sounds like you have a distributor ignition inline 4 or six from the early to mid 70s.

If you are using a non-merc tach, the brown wire would go to the AC side of the rectifier. Only the older tachs used switchbox signal. Assuming I am correct in predicting the year and type of ignition, the switchbox gets a red wire, always +12VDC, and the white wire from the ign key.

 

[Rip n Lips]

Re: Internal Wiring Harness

Jerry, It would help f you told us the year and model of your motor. It sounds like you have a distributor ignition inline 4 or six from the early to mid 70s.

If you are using a non-merc tach, the brown wire would go to the AC side of the rectifier. Only the older tachs used switchbox signal. Assuming I am correct in predicting the year and type of ignition, the switchbox gets a red wire, always +12VDC, and the white wire from the ign key.

You are correct, it is a 75 Merc 115 Inline 6. According to the CDI instructions that came with the harness, the red 18awg wire goes to the positive post on my rectifier and "may not be needed". There is a red 18awg jumper wire which the directions say to connect between rectifier positive post and the red terminal on the switch box. As of right now I have the red wire from the harness connected to the rectifier...Should I disconnect that wire and tape it off and just use the jumper wire instead? The orignial harness had a wire that went directly to the rectifier that's why I connected that one instead of the jumper... Can you tell me which terminal on the switch box the white wire from the ign. key goes to? I will try to post a pic of the switch box asap. Thanks.

 

[Chris1956]

Re: Internal Wiring Harness

Jerry, If you really have a 1975 Merc 1150, it's wiring is a bit different than the later models, according to my OEM Service Manual. The switchbox seems to have: (from the bottom starboard side, going up) white wire -red wire-brown wire -green wire to coil. The brown wire needs to be moved to one of the AC wires of the rectifier. Connecting it to either yellow stator wire will work.

It was hard to follow your description of the red +12V circuit, however, the red +12V circuit needs to connect the battery to the switchbox and rectifier and provide power to the keyswitch. The connection between the battery and the red wire of the engine harness should be made at the plug. If you have two red wires in the enginer harness, connect one to the switchbox and the other to the rectifier +DC pole. If not, use the red jumper wire to connect the rectifier to the switchbox, and connect the engine harnedd to the switchbox to complete the circuit.

 

[Plainsman]

Re: Internal Wiring Harness

Jerry when you say red jumper, do you mean that it splits off of one red wire into 2 wires so that it looks like a Y? If so, one red to the rectifier and one red to the switchbox.

 

[Rip n Lips]

Re: Internal Wiring Harness

Jerry when you say red jumper, do you mean that it splits off of one red wire into 2 wires so that it looks like a Y? If so, one red to the rectifier and one red to the switchbox.

No it doesn't Y, it's just a 12" long 18awg wire that is not connected to the harness. It has a connection at each end and would be used to complete a circuit from the rectifier to the switch box.

Chris thank you for your help, I guess I should probally break down and buy a service manual for it. So by taping off the red wire that comes out of the wiring harness, and by using the red jumper instead, going from the rectifier to the switch box the rectifier will provide power to the switch box correct? Thank you for your help.

 

[Rip n Lips]

Re: Internal Wiring Harness

Here is a pic of the switchbox. You can see the only new wire that is hooked up is the brown (tach) wire. So according to your directions Chris, I should have the Red JUMPER wire from the terminal below the brown to the Rectifier, then the White (12v from key switch) connected below that on the bottom most terminal?

 

[Chris1956]

Re: Internal Wiring Harness

Rip, You need to connect the red wire from the harness to the switchbox. Now use the red jumper to connect the switchbox to the rectifier. The orange wire is unused.

BTW your picture of the switchbox exactly matches the wiring diagram I have for your motor, and this wiring was only used for the 1975 1150.

Strangely, the '73 850 and the '77 1500 Mercs I have are wired differently than yours. The '73 850 has the same big ugly red coil and rectifier that you have, while my '77 Merc 1500 has the newer small coil and small rectifier.