1978 swithch box - power in - no pwr to ign coil

[samm835]

I have been trying to go through my motor and figure out why I can't get spark to my plugs. My motor doesn't have a trigger. I have a distributor, and ignition coil, I have read that you need a DVA meter. I am sorry I don't currently have a manual(one is on order). I have a meter, and tested power coming into my switch box(12V), but the terminal going to my ignition coil doesn't have any power at all. I am guessing that this is my problem......the switch box has gone out? Damn that's an expensive part to go out (460). BTW the motors wires have mostly been replaced and a new stator installed. Will someone help telling me I am prob correct assuming the switch box is out since that terminal has no power coming out? Also, does anyone know where one can be bought for a lot cheaper? I have looked on CL for a used parts motor but so far a no go, also anyone know what other years and HP I can use that will interchange with my 1978 90 HP 6cyl? Thanks

 

[narvlebenoit]

Re: 1978 swithch box - power in - no pwr to ign coil

You can try eBay.you only have one switchbox on that motor.I have a 1981 model it has two switchboxes I bought two at BoatFix.com for 140.00 a peace.

 

[Moody Blue]

Re: 1978 swithch box - power in - no pwr to ign coil

Confirm you have a single coil with distributor? You do have a trigger, its built into the distributor.

The output from the switchbox to the coil is a pulsed high voltage. Its is timed by the trigger circuit in the distributor. Not likely to read it using just a voltmeter.

This is the wiring diagram for your motor

http://www.maxrules.com/oldmercs/Wiring/1966ona/50.jpg

Make sure you have +12V on the white and red wires at the non-distributor side of the switchbox.

Disconnect the mercury tilt switch, they sometimes go bad preventing the engine from firing.

You can go here to read about testing the switchboxes.

http://outboardparts.com/mercury/troubleshooting/troubleshooting8.htm

http://www.boatpartstore.com/page18.asp

http://www.maxrules.com/cdi/TroubleshootingGuide.pdf

 

[samm835]

Re: 1978 swithch box - power in - no pwr to ign coil

Thanks for the help, I did notice my "mercury switch" wasn't hooked up, I bought this motor a short while ago and to be honest If I remember correctly it was running with it disconnected. Where should this be hooked up to? It has two wires, one is bolted to the frame grounded, the other is just dangling. Is the mercury switch my tilt switch? What else should I be looking at before buying a switch box? Help is so much appreciated!!

 

[quantumman29]

Re: 1978 swithch box - power in - no pwr to ign coil

hey man,
I just ordered 2 switch boxes for my 1985 merc tower of power from this place,
they cost 65$ a piece.....

http://www.outboardexchange.com/

I hope this helps you out, I nearly sheet a golden goose egg when i found out they were 425$ a piece,whew thank god I found this place...

mike

 

[Moody Blue]

Re: 1978 swithch box - power in - no pwr to ign coil

Thanks for the help, I did notice my "mercury switch" wasn't hooked up, I bought this motor a short while ago and to be honest If I remember correctly it was running with it disconnected. Where should this be hooked up to? It has two wires, one is bolted to the frame grounded, the other is just dangling. Is the mercury switch my tilt switch? What else should I be looking at before buying a switch box? Help is so much appreciated!!

Refer to the wiring diagram link I gave you to see where the mercury switch is hooked up. Yes it is the tilt switch. Automatically kills the ignition if tilted up too high.

Before spending a dime, I'd invest some time testing your existing switchbox to be SURE it is bad before spending the money on a new one.

 

[samm835]

Re: 1978 swithch box - power in - no pwr to ign coil

Thanks moody, I looked through your attachments and hooked the merc switch back up and It didn't seem to make any differences. I am going to go through your links to try more testing on my switch box, the switch box looks really bad on the side that my distributor is connected to. I will try more testing once I read everything, does the mercury switch only keep the motor from starting if the motor is tilted? I don't have the motor tilted so that shouldn't be a factor right? As of right now the switch isn't even hooked up. Thanks I will post my findings later.

 

[rodbolt]

Re: 1978 swithch box - power in - no pwr to ign coil

carefully test the switchbox, there is a method to bypass the trigger and test output but I cant remember it.
you think the switch box is pricy try the trigger and the 4 to six hours it takes to change it.
do NOT atempt to pull the rotor from the shaft or you will post abot how much they cost and how long it takes to replace it.

 

[samm835]

Re: 1978 swithch box - power in - no pwr to ign coil

Thanks for all the help....I am going to have to take it to someone I think. I can't figure jack out on how to properly test it. As much as I hate it....I think at this point I am going to need to pay someone to properly test it to figure out what is broken. You can see the attached picture that the switch box isn't in great looking shape. I didn't hook the mercury tilt back up permanently because it will worka apparently without it. Thanks I will update as soon as I get the money to take it into a shop. Again thanks for all the help.

 

[usskydvr]

Re: 1978 swithch box - power in - no pwr to ign coil

To test your switchbox disconnect the 3 dist wires ( be sure to put labels on them so you put them back correctly). Jumper the brown to white terminal on the switchbox. Then turn on the ignition switch. Each time you touch
the black terminal to ground you should get a spark. If you do the switchbox is good and the trigger is bad. If no spark, the switchbox is bad.

 

[usskydvr]

Re: 1978 swithch box - power in - no pwr to ign coil

p.s DO NOT 'connect' the Black switchbox terminal to ground, only touch it to check for spark.

 

[samm835]

Re: 1978 swithch box - power in - no pwr to ign coil

USS, let me make sure i understand correctly. Disconnect the distributor wires (3), now the brown wire i just disconnected....attach that to where the white wire was? Do I try to start it after doing this? Also I know i sound like a damn fool, but I am not following you on the ground portion of your txt. Do I take an extra wire.... and ground it...then touch it to the black terminal wire location? thanks

 

[usskydvr]

Re: 1978 swithch box - power in - no pwr to ign coil

To clarify. When doing the test all three wires to the dist are not connected to anything. The jumper goes from the Brown Terminal on the switchbox to the White terminal on the switchbox.

 

[usskydvr]

Re: 1978 swithch box - power in - no pwr to ign coil

p.s. You are correct. Take an extra wire and attach it to ground. When you touch the other end of this grounded wire to the Black terminal on the switchbox you should get a spark.

 

[samm835]

Re: 1978 swithch box - power in - no pwr to ign coil

Please don't think your talking to a third grader(i might sound like it though)....but I am just making sure I don't burn something else out. I VERY MUCH appreciate all your help, I am hooking a wire to the brown terminal(dist side) and hooking it straight to the white wire (side where starter is), then I try to start the motor correct? I am not second guessing you, but if my distributor is disconnected how will the plugs get spark to start? I know your prob thinking....wow how can this guy walk and chew gum.

EDIT: Ok after re-reading I think I now get what you are saying.
1) disconnect the dist wire completly, take an extra wire install it from white to to brown(all on dist side).
2) take an extra wire and ground it, and turn ignition to the start position and then ONLY touch the black terminal post

If I get a spark then switch box is good....and more than likely my distributor/trigger is gone. please let me know if I have this in the right order. Thanks and sorry to be a pain in the *****

 

[usskydvr]

Re: 1978 swithch box - power in - no pwr to ign coil

No,,,no... not the starter side. Before you disconnected anything, the three wires from the dist should all go to the same side of the switchbox ( the dist side, not the starter side). See the attached wiring diagram. You do not try to start the engine. You only turn the iginition switch to 'on' NEVER 'start' AFTER you have put the jumper from the Brown terminal on the switchbox to the White terminal on the switchbox. When you touch the Black terminal on the switchbox to the wire you added and that is connected to ground, it will cause the switchbox to send a high voltage signal to the coil which is connected to the center of the distribitor cap. Inside the distributor cap the rotor will send the spark to one of the spark plugs. (p.s. you need to have one of the pistons near or at the top of their stroke. you can do this by removing any one of the spark plugs and rotating the flywheel until you can see the piston. a small flashlight will help)

 

[usskydvr]

Re: 1978 swithch box - power in - no pwr to ign coil

attachment

 

[samm835]

Re: 1978 swithch box - power in - no pwr to ign coil

Ok now after following all USS instructions.....I found out when I touch the black wire with the ground axtra wire....it sparked a little. So I was done doing my testing for the evening, I cleaned all the wires and hook ups, and thought to myself, what the heck why not try and start.....low and behold the freakin monster started on the first try! So I am guessing after all my testing I should have listened to the post about always cleaning terminals first! Thanks for all the great help!