1977 Mercury 115 Switch Box Troubleshooting

[tavacska]

The outboard motor I got has no ignition for all cylinder.

I did the following test.

1. I first take off the switch box and connect the switch following attached test diagram. Jumper the red and white with 12 v. Then jumper the brown and white. There is good fire between the high tension lead from the ignition coil and ground.

I wired the switch back to the motor following the diagram except that I jumper the red and white with 12v and disconnect the tilt switch as many recommended. And I disconnect the wires from rectifier.
2. Check the DC between red and ground, it reads 12.5 v.
3. Check the DC between brown and ground, it reads 12 v.
4. Check the DVA between white and black trigger wires, it reads 0 v.
5. Check the DVA between green and ground and then manually crank, it reads 0 v.

Can I confirm that the switch is bad? Can I repair it or just have it changed?
My test #1 passed and I was so happy about that. But it seems the white and black triggers are the bad ones. Am I right?

 

[merc850]

Connect the rectifier back up before doing anymore testing - you could damage it. If the Nr. 1 test is OK and you get spark from touching the black wire to ground then the problem is probably the trigger in the distributor, or, the cap is faulty - take it off and look for a carbon brush in the middle that touches the rotor; I bought an 850 last summer and the brush was gone!

 

[tavacska]

Connect the rectifier back up before doing anymore testing - you could damage it. If the Nr. 1 test is OK and you get spark from touching the black wire to ground then the problem is probably the trigger in the distributor, or, the cap is faulty - take it off and look for a carbon brush in the middle that touches the rotor; I bought an 850 last summer and the brush was gone!

Thanks for advice.
But the DVA between white and black is 0 when the wires connected with distributor. The manual said it is wrong with the switch. Is that right?

 

[merc850]

Did you connect the white wire to the side of the SB with the red one? that's the wire that powers the ignition (+12v) when you turn the key to "RUN". Are all your ground wires connected and hooked up to battery. I traced my trigger problem by using your 1st diagram not by DVA readings.

 

[tavacska]

No Title

Yes. I did jumper the red and white lines with +12v. And the ground points all over the motor all good with battery negative post.
From the instructions, it seems to check the white and black on the trigger side too.

But anyway, I will open the distributor cap up to do some inspect.

 

[tavacska]

So the trigger fails means the white and black lines from distributor fail?

How do I fix the trigger issue?

 

[merc850]

If the trigger itself is bad you have to replace it http://www.iboats.com/Mercury-Marine...view_id.696947 is the part, (maybe cheaper at a dealer, ebay,) if the wires are broken or corroded you might be able to splice in new ones.

 

[tavacska]

Then it must be the trigger. The wires look good to me.
Thanks for the advice.