New wiring harness for 1979 70hp?

[WillaminaOR]

If I'm dating the motor right it's a 79 Mercury 70hp. It came on an 81 Sea Nymph boat I bought. I was told it had good compression and it looks like it's in decent shape to me. The issue is the wiring harness has corroded where some of the wires are falling apart. When I look at parts diagrams, find the harness, and look up the part number it says NLA. Google doesn't seem to show an aftermarket replacement either. Is there another harness that will fit or can be adapted fairly easily?

 

[racerone]

Contact---CDI----electronics.-----They may be able to help.

 

[Chris1956]

I did not see on on the web either. That was surprising as I had bought a harness for my old '77 Merc, likely in the early 2000s and had no issue finding one. Flea Bay is sold out, but they could get more.

If the quick disconnect plug is good, you can cut the wires off and solder and shrink tube new ones, If the plug is bad, then you will need to find a male and female plug and replace both ends of the harnesses.

Alternatively, you could buy a new wiring harness from the control to the motor with the round plug and pick a newer ADI harness from a Merc engine and adapt it. Your harness likely has battery, ground, ign killer, ign power, choke, tach sender and overheat wires. A newer harness likely has the same and may have PTT wires also.

 

[WillaminaOR]

I did not see on on the web either. That was surprising as I had bought a harness for my old '77 Merc, likely in the early 2000s and had no issue finding one. Flea Bay is sold out, but they could get more.

If the quick disconnect plug is good, you can cut the wires off and solder and shrink tube new ones, If the plug is bad, then you will need to find a male and female plug and replace both ends of the harnesses.

Alternatively, you could buy a new wiring harness from the control to the motor with the round plug and pick a newer ADI harness from a Merc engine and adapt it. Your harness likely has battery, ground, ign killer, ign power, choke, tach sender and overheat wires. A newer harness likely has the same and may have PTT wires also.

I looked up CDI electronics and it looks like they don't make the harness any longer. You said ADI but I think that's a typo?

I may be able to repair the original harness but it's in really bad shape. The other issue is that I don't have forward controls either so what ever I do I'll have to find matching controls (plug). I'm an electrician, but inside wiring type, not auto or marine, so I'm probably capable but out of my element. Is there a good diagram + pictures of the harness and how it fits? When I bought the boat the harness had already been removed and spread out and attached to a board, I guess for repair.

Thanks,
Bryan

 

[Chris1956]

ADI (alternator driven ignition) is the type of ign system that you have, versus battery powered CDI (capacitive discharge ignition). CDI Electronics is a company that makes lots of replacement ign parts.

If you need controls, you also need a boat wiring harness. The newer controls are mechanically compatible. The wiring harness will be electrically compatible, but with a round plug of roughly 1-1/4" in diameter with 7 male pins,1 female pin and likely 2 bullet connectors. So it looks like the simplest plan is to get a new engine harness as well, as it will have the patching plug.

Mercury motors from the 90's have the correct plug. I am not sure of the exact range or years that have the correct plug, but my 1993 Merc has it. One would think that a harness from a 3 cylinder Merc from the 90's would be adaptable or your needs. Sorry I cannot be more help.

 

[merc850]

Post a picture of the plug and the serial Nr. I think it uses a flat plug inside the cowling.

 

[racerone]

Make your own harness.--------Simply bypass the plug at the motor and put all wires on a terminal strip.

 

[Chris1956]

As Racerone says. You can make your own. You should have the old wiring harness colors. So, red is battery positive, Black is battery Neg., choke is grey. Ign power is white, Starter solenoid is yellow, tach sender is brown, Ign killer wire is salmon or orange.