1983 Mercury 70hp EL no FIRE

C

Corrupt

Cadet
Joined
May 31, 2012
Messages
20
I've been working on a friend of mines pontoon boat that we had to replace the motor on due to a cracked head. He bought a used '83 mercury 70hp motor to replace it with. We installed it and it ran fine for a couple times, then we got into this no-run issue. It will crank but not run.

I checked for fire and we didn't have fire, so checked out the stator and it seemed to be grounded out. So we pulled it off and while in there i noticed the triggers had this black gooey residue, so we decided to replace the stator AND the triggers. After installing the new items, we still had no spark. we picked up a switchbox and replaced it and still no spark.

All testing above was done with the 2 yellow wires from the stator disconnected and connected, and also the kill switch was disconnected. All grounds have been checked and cleaned. Also new spark plugs are in.

It was getting late and the battery we were testing with was running low on juice. Could a low battery not spinning the motor fast enough cause a no fire situation? There at the end it was getting to the point that it was spinning slow enough that the started would disengage.
 
Last edited:
I

Iron Pony

Recruit
Joined
Sep 3, 2013
Messages
2
Re: 1983 Mercury 70hp EL no FIRE

Silly question, have you double checked the emergency kill switch?
If not that, about the only thing left is the coil packs.
 
C

Corrupt

Cadet
Joined
May 31, 2012
Messages
20
Re: 1983 Mercury 70hp EL no FIRE

yes, both the kill switch and the "mercury" switch were both disconnected. I thought about the coil packs but why would all 3 go out at the same time?
 
C

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: 1983 Mercury 70hp EL no FIRE

A low battery , worn starter, or poor battery cable connection can cause a 'no spark' condition as the system has a minimum 300 RPM for the stator to generate sufficient voltage to the switchbox.

The switchbox has a black wire with a thin yellow line conning it to the wiring harness. This is the 'Ground-to-Killl' wire going to the ignition switch and safety lanyard switch. Disconnect this wire at the motor and retest for spark, if you now have spark then look for a ground somewhere on that wire killing your spark.
 
C

Corrupt

Cadet
Joined
May 31, 2012
Messages
20
Re: 1983 Mercury 70hp EL no FIRE

CharlieB said:
A low battery , worn starter, or poor battery cable connection can cause a 'no spark' condition as the system has a minimum 300 RPM for the stator to generate sufficient voltage to the switchbox.

The switchbox has a black wire with a thin yellow line conning it to the wiring harness. This is the 'Ground-to-Killl' wire going to the ignition switch and safety lanyard switch. Disconnect this wire at the motor and retest for spark, if you now have spark then look for a ground somewhere on that wire killing your spark.
Click to expand...

Battery sat on charge overnite. The black with yellow stripe wire has been disconnected during all our testing. Tried to start today and still no fire. Starter sounded strong and was spinning just fine. Thinking we may have got either a bad stator or a bad trigger sent to us. Would there be any reason as to why all 3 of the coil packs would go bad?
 
C

Corrupt

Cadet
Joined
May 31, 2012
Messages
20
Re: 1983 Mercury 70hp EL no FIRE

OK, I checked the voltages on the red and blue wires of the stator today. I'm getting 180volts while trying to crank on the blue wire. But Am getting no voltage reading from the red wire. This is testing on the new stator. So I took this stator out and put the old one back in. I'm getting the exact same thing on the old stator. Could there be an issue somewhere else that I'm missing? Or did I receive a brand new stator that has the same issue that my old one has?
 
ajgraz

ajgraz

Lieutenant Commander
Joined
Mar 1, 2010
Messages
1,858
Re: 1983 Mercury 70hp EL no FIRE

Are you using a DVA (adaptor), or a regular DVM / VOM meter? Red wire is connected to the high speed windings, you might not get any appreciable voltage reading from that at cranking speed, especially if not using a DVM. The high-speed windings (red) takes over at IIRC around 1500-2000rpm from the low-speed windings (connected to blue wire).

You say you got a replacement switchbox and a replacement trigger, were these new or used? CDI or new-old-stock (i.e., 80's vintage) or Sierra or ???
 
Last edited:
C

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: 1983 Mercury 70hp EL no FIRE

IIRC you will only get about 40 volts on the high side while cranking. Could be hard to see depending on the meter setting.

What does CDI list as minimum voltage cranking? Slow cranking from a dirty cable connection anywhere or an aging starter with a dirty comm and worn brushes and dry bushings may have the motor cranking at what may seem a fair speed, but 250 RPM is not enough voltage generated for the ignition system to function.

Load test the battery, just because it has been on a charger all night still does not ensure it is capable of cranking the motor sufficiently.
 
C

Corrupt

Cadet
Joined
May 31, 2012
Messages
20
Re: 1983 Mercury 70hp EL no FIRE

Replacement trigger, switchbox and stator are all new. CDI

Also, the guy that has been working on the motor was using an analog meter while testing the switchbox wiring to see if the needle would bounce up then back down. What he found right off the bat was that the needle was swinging backwards when trying to crank. He did have the wires hooked up correctly for the needle to bounce forward, but instead the needle went backwards. What would cause this?
 
Last edited:
C

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: 1983 Mercury 70hp EL no FIRE

Stator and triggers generate AC voltage, most meters will not register if turned to DC, however, when an analog meter attempts to swing left, below zero, that usually is caused by a DC setting and negative voltage. He may have the meter set to DC and attempted to measure AC voltage.

An analog meter set to AC and using a DVA Adaptor will work fine to test these ignitions. Without the adaptor the readings may NOT register at all unless the meter is set to a very small scale, which then is a risk of hurting the meter.

Inspect both stators along the outer edge, if the upper crank bearing is loose the crank may 'waver enough for the flywheel to contact the stator and cancel any generation.
 
C

Corrupt

Cadet
Joined
May 31, 2012
Messages
20
Re: 1983 Mercury 70hp EL no FIRE

Is there a way to test the coil packs, such as removing a wire from one place and tapping it on the + side of one of the coils to see if it will spark?
 
C

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: 1983 Mercury 70hp EL no FIRE

Corrupt said:
Is there a way to test the coil packs, such as removing a wire from one place and tapping it on the + side of one of the coils to see if it will spark?
Click to expand...

A DVA meter and following the tests spelled out in the CDI Ignition Guide will clearly show what the problem is.

ISSUU - CDI Electronics Practical Outboard Ignition Troubleshooting by CDI Electronics

One of the tests measures the output of the switchbox to the coil, if no output then test the stator and trigger, IF both pass the test then the switchbox is suspect.

But you MUST use the correct meter or a DVA adaptor. Any other meter alone casts suspect one the tests and are NOT RELIABLE.

Update your location, perhaps another member is nearby with a good meter/adaptor.

An adapter can be built surprisingly cheaply

Simple, easy to make DVA adapter for standard Multimeter?/ 374544
 
C

Corrupt

Cadet
Joined
May 31, 2012
Messages
20
Re: 1983 Mercury 70hp EL no FIRE

Well, we finally figured it out. Whenever I could I would go over and assist the guy working on the boat, and for the longest time we couldn't figure it out, but after checking the switchbox that was on the motor we figured out that we had power going to the switchbox but not coming out. He had a new switchbox that he had had on the shelf for about a year and we put it on, still nothing after the switchbox. He remembered he had another motor (6 cyl) in the back that might have the same switchbox in it. It did, so we put that in and it fired right up with the 1st turn of the key. So now my friend has the boat back at his house getting her all cleaned out and ready to go on the first run after a complete rebuild of the lower unit and also brand new stator, triggers, and a used switchbox. Also all the wiring got redone as the old wires were coroded.

I think before we go any wheres though, we'll put her on the muffs and make sure she pees.....lol
 
Last edited:
You must log in or register to reply here.
Top