1979 Mercury 90HP Ignition switch wiring

[kdenfan]

I received the switch today and I will put it in this weekend, but there is only one problem, I am not positive which wires go exactly where on the new ignition switch. The new switch has 5 terminals and they are labeled as Battery, Solenoid, Magneto, ACC and Ground. The ground is obvious and I believe the Battery goes to the Red wire on the wiring harness, but the other ones I need answers on. My Mercury is an L6 90HP 1979 (it is listed in my manual as 1979 only) it has the orange color wire going to the Mercury switch and switch boxes and not the yellow and black wires found in other years.The old switch isn't labeled the same and I really want to make sure that I get this connected correctly the first time (no electrical fires). My old switch has 7 wires 2 white (I believe acc's), 2 black (ground), a yellow ( I think this one is the solenoid), Orange (maybe Magneto???) and the red(battery). Can someone please verify these for me and let me know if this is correct. Thanks for all of your time and help I do really appreciate all the feedback.

 

[Chris1956]

Re: 1979 Mercury 90HP Ignition switch wiring

The wiring harness should have Grey(choke), red (+12VDC), Black(ground), yellow(solenoid), White (ign +12VDC accessory), orange (ign killer wire). The last five go on the ign switch, if you have the seperate choke switch.

One of the two black wires is likely a brown wire for the tach signal. The tach signal wire will run to the rectifier. You might test it.

I also assume one of the white wires is really a grey for the choke solenoid.

 

[kdenfan]

Re: 1979 Mercury 90HP Ignition switch wiring

ok, so now I have it hooked up as explained, however, now my choke only works in the acc. position and not when the ignition is in the run position. I also still have no spark, but when the black/yellow [orange on my model] wires are disconnected at the switch boxes, I have spark but if I disconnect the orange wire at the ign. switch I have no spark. I went through my wiring harness at the powerhead and replaced some badly corroded wires and when I did I found that the connector to the mercury swich was grounding out. I corrected this, but I haven't hooked it back up yet. On my ignition switch it is labeled magneto, is this where the kill wire is supposed to be installed? Is my choke supposed to be hooked up to the acc. switch, or to the red 12vdc [I think] it is supposed to be to the acc. but I am not sure why my choke isn't staying on in the run position. Any suggestions will be appreciated and followed. Thanks.

 

[Chris1956]

Re: 1979 Mercury 90HP Ignition switch wiring

On and accessory should be the same on the ign switch. Choke should work in the run positon, as well as in the start position. It is a merc Ign switch right?

Mag is where the orange wire should be connected. it sounds like the orange wire is grounded somewhere in the harness. You need to find and fix that.

One side of the choke button should get the white accessory wire, and the other side should get the grey choke wire.

 

[kdenfan]

Re: 1979 Mercury 90HP Ignition switch wiring

the ignition switch is aftermarket, made by Sea Dog model number 420351-1. It was the only one available for my year make and model, from iboats. It won't fit into the control box, so I will be forced into moving it up by the steering wheel. I called iboats customer service before ordering and they said that is what they had for my application. I guess I should have looked elsewhere. I think I still will. So if the choke is attached to th acc. terminal, should there still be 12vdc power to it even while cranking the engine? If so then something is a miss some where. I will put it back together and test it out and let yoy know of my findings. Thanks.

Update, I can't find a switch that isn't "push to choke" would it be easier to convert to this style or try and get one with just 5 terminals rather than 6 with the PTC option. My original number on my switch is 129 C51015 and it looks original. 5 terminal, yet 7 wires(2 black and two white, one coming from the choke button and one going to the powerhead)

 

[kdenfan]

Re: 1979 Mercury 90HP Ignition switch wiring

I hooked everything back up and the boat started. I still do not have voltage at the acc when I turn the key to start. I had to manually adjust the choke. I hooked a multimeter up to the acc while attempting to start it...voltage in run/on and no voltage in start. I will not put it back together until I figure this out. Where does the white wire attach to at the power head (engine) end? In the manual it shows it reaching the end of the wiring harness, but it does not connect (or cross over) to the actual engine side. Is it tied to the red 12vdc at the end of the harness? If so there should always be 12vdc, correct? Let me know what you think and once again thank you Chris. I still can't locate the actual original Mercury switch any where on line with out the push to choke option.

 

[Chris1956]

Re: 1979 Mercury 90HP Ignition switch wiring

I don't think the white wire goes all the way to the motor, on that ADI ignition.

It does sound like the wrong ign switch. Do you have power on any switch pole in the run and start position? If so, you could use that to power the choke switch. If not, connect the choke switch to the red wire. It won't use any power when the choke is not active.

 

[kdenfan]

Re: 1979 Mercury 90HP Ignition switch wiring

That is exactly what I am going to do Chris. I am now just going to abandon the acc terminal and hook up the choke/trailer/tach to the red/battery terminal, I have already hooked it up that way temporarily and it seems to work fine. I am also considering hooking up a seperate choke switch up by the new ignition switch (on the dash board), just to make things easier to reach when I have to use the choke. I also agree that the white wire must not have been for my engine, as there are only 6 terminals on the wiring harness in the engine, yet 7 terminals from the control box harness. I think that almost all of my problems really stemmed from bad wiring inside the engine itself, they were all severely corroded and all of the insulation was falling off. I had mended it about a year ago, but I didn't really fix it until I pulled the whole wiring harness out and rewired the entire thing and that is when I noticed the "kill switch" was grounding out. This forum has got to be the best online help that I have ever experienced so far, everyone has been so helpful and patient with answering all of my questions. Thanks again. Now I can get back to the original thread (1979 90HP Mercury flodding issues) and go from there. Next step is to take the boat to the water and perform the final steps of Link and Synch. I will keep posting until I am done. Thanks again.

 

[Rojolo]

Re: 1979 Mercury 90HP Ignition switch wiring

Hi, I'm having a similar problem. I am trying to hook up a sierra 4100 ignition switch with a push in choke to a '79 90HP Tower of Power with distributor-less ignition. The terminals on the switch are marked M,B,M,I,S, and C. In my manual they are marked A (red), B(yel), D(blk), E(orange) and F(white). My harness has 7 wires coming from it. the five colors listed previously and 1 gray and 1 brown. I have it hooked up as M(bk), B(rd), M(or), I(yel), S(wh), and C(gray) per manufacturers instructions. The problem I'm having is after the motor starts the pinion gear drops out of the flywheel but the starter motor keeps on spinning. Is this the correct switch for this application? Did I possibly connect the wires incorrectly? Could my starter be bad? Is the ignition switch faulty? Any help with this issue is greatly apprecciated!

 

[Chris1956]

Re: 1979 Mercury 90HP Ignition switch wiring

The switch is fine. You have the wires switched, I will bet. Starter solenoid is yellow, it should be on S. White is +12VDC accessory. It should be on I

 

[Rojolo]

Re: 1979 Mercury 90HP Ignition switch wiring

Thanks Chris, The starter problem is solved, however the problem I'm having now is the only way the motor starts and runs is if I shoot starting fluid into the carbs. I have a full tank of gas, the carbs are clean and the fuel pump is working. I didn't connect the Brown wire (tach?) is this wire neccessary to keep the motor running? If so which terminal would you suggest to connect it to? Thanks Again for all your help with the starter issue, Bob.

 

[Chris1956]

Re: 1979 Mercury 90HP Ignition switch wiring

The Brown wire is simply the tach signal. It will have no effect on the motor's ability to run.

Does the choke work? The carb shutters should close on the top two carbs, when you push to choke. If not the wiring is bad or the choke solenoid is bad. Choke wire is grey...

 

[Rojolo]

Re: 1979 Mercury 90HP Ignition switch wiring

The Brown wire is simply the tach signal. It will have no effect on the motor's ability to run.

Does the choke work? The carb shutters should close on the top two carbs, when you push to choke. If not the wiring is bad or the choke solenoid is bad. Choke wire is grey...

Yes, the choke works fine. Upon further examination the needles and seats are very badly worn on 2 of the carbs. I have ordered rebuild kits for all 3 carbs and I'll post my progress in the near future. Thanks for all of your help

 

[jeremyfowler]

Re: 1979 Mercury 90HP Ignition switch wiring

Yes, the choke works fine. Upon further examination the needles and seats are very badly worn on 2 of the carbs. I have ordered rebuild kits for all 3 carbs and I'll post my progress in the near future. Thanks for all of your help

i have a question about a 1996 mercury 50hp wiring harness. i just purchased one from merc dealer and am trying to install it myself, and am having no luck! all ican get from it is the alarm buzz, and thats when i am trying to start it, yet the motor is dead, wont turn over or nothing. the wiring harness comes with the ignition to, all in one type deal. so, there are 8 wires i still have to hook up, they go to the kill switch,trim/tilt and alarm. they are two purple wires, two yellow/red wires, two black/yellow wires, a tan/blue wire and a black wire. does any one know how these wires tie in together???? its an 8 point harness with a push in choke in the ignition switch.