1982 Mercury 70 hp appears to have no spark...

[goosemanhnt4fud]

Yesterday morning I took the boat out and it ran fine. Yesterday afternoon I took it out again, and it would not start. Today I tried to trouble shoot it. This is what I did:

1. Fuel pump is working, removed the line from pump to carbs,(carbs were cleaned two weeks ago) and it is squirting out gas.
2. Compression check is 146/146/147
3. I removed the spark plugs, and they were dry. I squirted some fuel in the #1 and #2 cylinders and tried to start it, but it would not fire.
4. I made sure the kill switch was in the run position.
5. The inline fuse on the hot wire that goes to the rectifier, fuse is good, and as I attempt to start the yellow wire that goes to the stator has power. (the stator does have some dry rotted wires)
6. all three spark plugs are new
7. Took a spark plug out, and turned over the motor and saw no spark.

What is my next step? Is there anything else I should look for?
Thanks in advance.

 

[PHE]

Re: 1982 Mercury 70 hp appears to have no spark...

If you don't have spark on any plug it is the switchbox, stator,or trigger along with their associated wiring, or something is grounding the kill terminal on the switchbox.

 

[goosemanhnt4fud]

Re: 1982 Mercury 70 hp appears to have no spark...

Thanks for the reply....I take it the kill terminal is a location on the switch box, which one would it be on this picture of the switch box. would it be possible to try to track the wire back to where ever it goes and look to see if it is frayed??

How hard would it be to change the stator and trigger??

 

[PHE]

Re: 1982 Mercury 70 hp appears to have no spark...

The kill terminal is the second terminal from the top left. It floats when running and is grounded by the key switch or mercury switch to turn the motor off. Any voltage applied to this terminal will kill the switchbox. I had a harness short that applied 12VDC to it when I pressed the choke button and it cost me a switchbox. Good thing I checked it out before I blew the new one.

You have to remove the flywheel to get to the stator and trigger. There is a handy tool that is both a lifting eye and flywheel remover that is reasonably priced on ebay for this. Of course, you only need it if they are defective.

Get a manual and work your way back to find the problem. Test if you have spark on any plug. If not, I wouldn't think that all coils are bad, so you are back to the switchbox. Test if the trigger and stator are working. If they test OK, it is the switchbox. If that is the problem, try to figure out what blew it.

Hope this helps.

 

[goosemanhnt4fud]

Re: 1982 Mercury 70 hp appears to have no spark...

Is there a method to testing the stator and trigger?

I have a Clymer manual, it came with the boat/motor. It shows the wire diagrams and such in the rear of the manual...so I can use it for reference, the manual reaflly doesnt have a troubleshooting section....

Do switch boxes just go bad sometimes or are they pretty sound until you electrically fry them?

 

[goosemanhnt4fud]

Re: 1982 Mercury 70 hp appears to have no spark...

Would it be possible to by-pass the kill terminal and try to start the motor to completely eliminate the kill switch being a part of the problem?

I was thinking of taking the wire off that terminal to see if the motor would start??? Any thoughts on this?

Thanks for all the help so far.

 

[ajgraz]

Re: 1982 Mercury 70 hp appears to have no spark...

Yes, just undo the ring terminal from the kill circuit at the switchbox (either black/yellow or orange wire, can't recall which for your year) and the kill circuit is out of the equation.

Bear in mind that if the motor does start, key-off will not shut off the motor if you remove that circuit. You can choke it to shut off or just disconnect fuel line and let the carbs run out.

 

[goosemanhnt4fud]

Re: 1982 Mercury 70 hp appears to have no spark...

Thanks, I will give it a try...

 

[goosemanhnt4fud]

Re: 1982 Mercury 70 hp appears to have no spark...

Well, i tried the removal of the kill switch wire, from the switch box and the mercury switch and tried cranking her over...nodda...

I did notice the yellow wire from the stator, is almost completely dry rotted thru right at the stator...which i am assuming is not good...does anyone know what that wire is for, the purpose of it, it goes right down to the rectifier... ???

Looks like i need to purchase one...should anything else be changed along with the stator?

Thanks for all the help...

 

[ajgraz]

Re: 1982 Mercury 70 hp appears to have no spark...

Yellow wires from the stator send AC through the rectifier, which changes it to DC for charging the battery. Should not affect spark, and you could just solder in replacement wire if you can cut back enough to get to good wire...assuming the rest of the stator is OK.

You can do some checks on stator, trigger and coils with a standard resistance/voltmeter, but a thorough checkup of these parts requires a DVA attachment for your meter (about $30-$35 on the net). And there is no way to directly test the switchbox, that's just a matter of eliminating the other ignition parts as possible problems first.