1978 Mercury 80hp wiring harness question. Wiring new key switch.

[Basstrackerpro17]

I'm trying to wire up a new key switch to my 1978 Mercury 80hp motor. The motor has no spark at the plugs. I did some tests with an OHM meter. Looked at my engine harness wires and they were rotted. I replaced all 7 of the wires. Off the harness plug to the engine there are is big red and black wire for the battery. There are also 7 smaller different colored wires that run to the key switch and I think one of the 7 wires goes to the choke switch and one the the tach connector. That leaves five wires to wire to the key switch. I'm not sure where to connect the wires to the key switch because I'm not sure which one goes to the terminals marked ACC, GRD, MAG, BAT, and SOL. For example: Where does the red wire from the Rectifier hook to on the key switch? I have a drawing from maxrules.com but I'm not sure how to read the key switch diagram. Please help. Thanks.

 

[Chris1956]

Re: 1978 Mercury 80hp wiring harness question. Wiring new key switch.

Do you have a distributor on that motor? If so, I do not think it is a 1978. It is likely a few years older. The wiring is basically the same.

Black is GND, white is ACC, orange or Salmon is MAG, Red is Batt, Yellow is SOL. The choke solenoid is a grey wire. That should connect to the choke button. BTW - Salmon or orange wire is unused on distributor ign Mercs.

 

[Basstrackerpro17]

Re: 1978 Mercury 80hp wiring harness question. Wiring new key switch.

I believe I have the key switch wired right but I'm still not getting any spark at the spark plugs. I have tried some of the testing with an OHM meter. The coils and stator seemed to be in the reading range suggested. I tried removing the orange wire off the switch box then tried to crank the motor and still no fire. I did discover another orange wire hooked to nothing that I OHmed and it was inline with the orange wire off of the switch box. All spots on the switch box have single wires going to them and I'm not sure if this wire needs to be hooked up to anything. The rectifier has a red, 2 yellow, and I think brown wire going to the three terminals on it. Does anybody have any suggestions? Thanks.

 

[Chris1956]

Re: 1978 Mercury 80hp wiring harness question. Wiring new key switch.

You have not told me if that motor has a distributor or not. The troubleshooting procedure is dependent on that fact.

 

[mikesdealz818]

No it doesn’t no distrib it’s coils

 

[mikesdealz818]

I need a good clear picture of how the rectifier wires go on a rectifier and where those wires go to . And their two yellows on the stator wires one has a red line which one goes to which post on the rectifier

 

[mikesdealz818]

My engine turns over if I jump the starter silinoid and I had spark in cyl 1 it hits with starting fluid acts like it’s gonna start then immediately kills itself down from doing such .