1960 75 hp Evinrude distributor/magneto question

[bilbo1usa]

Hello all,
I've got an electrical issue on my '60 75hp. No spark. It was running poorly at high RPM (never sustaining full RPM) so I opted to redo the electrical after a total carb overhaul proved fruitless. When I opened the distributor, I found pieces if the spring that contacts the coil everywhere inside, and the clips that hold the coil in place were shattered.
I've replaced the coil(and the clips that hold it steady), plugs, wires, points & condenser.
Now I get no spark.
Great repair huh?

When I put the meter on the coil Hi-voltage output (the little brass nub on the top) and spin the shaft I get good readings. But when I put the cap on, I get nothing from the plug wires.

With the cap off I connected a patch wire from the brass nub on the coil to the little spring on the inside of the distrib cap that usually contacts the nub, I get a strong reading at the spring.
With the patch wire still in place, I looked for a reading at one of the 4 points inside the cap where the rotor passes, and I get almost nothing.
I assume the hi voltage from the coil feeds to the positive 2 of the 4 points via a wire molded inside the cap?

I've had no experience to this point with magneto style distributors, and this befuddles me, but I fancy myself handy enough to fix the issue.
Can the cap just suddenly go bad?
Is it wired internally, molded within the cap?

Any help would be appreciated.
Thanks all,
Bill

 

[1946Zephyr]

Re: 1960 75 hp Evinrude distributor/magneto question

I would go back and re-check all your work. It sounds like something isn't making the correct connection

 

[boobie]

Re: 1960 75 hp Evinrude distributor/magneto question

Dumb question. Is the rotor in the magneto?

 

[bilbo1usa]

Re: 1960 75 hp Evinrude distributor/magneto question

Yes, and honest question Boobie (maybe you're being a smart alec?)...
The rotor sits on the top of the shaft, in the distributor cap. That same shaft spins inside the magneto which is technically above the distributor.

And yes 1946 Zepher, the connections have all been thoroughly checked. Three times at least.
My wife is a retired electrical engineer and has been trouble shooting this with me, and I've got a lifetime of mechanical work under my belt, just not on two strokes, so the basics have all been covered.

I guess part of what is stumping me is the basic flow of the magneto design. Does the rotor receive power up the shaft from the stack of plates spinning in the magnets? Or does it spin the current that is being sent to the positive posts inside the cap from the coil?

Thanks guys.
Bill

 

[F_R]

Re: 1960 75 hp Evinrude distributor/magneto question

The housing is magnetic and the magnetic lines of force are completed through the laminated core of the coil. The rotor spinning inside it (the magnetic field) interrupts the magnetic lines of force, causing a CHANGING magnetic field across the primary windings of the coil---That is a generator in action. Furthermore, the many-turns secondary winding of the coil creates a transformer. High voltage is induced in the secondary winding when the points open which causes a collapse of the current in the primary winding. Your electrical engineer wife should understand that. The rest of us mere mortals may have a bit of trouble without a lot of study in electrical theory. Someday, I may write a book.

See your duplicate question in aomci Ask-A-Member. I explained the rest of the system over there.

 

[CharlieB]

Re: 1960 75 hp Evinrude distributor/magneto question

Is the rotor new?

A rotor can 'burn thru' grounding the current 'thru' the rotor to the shaft.

Remove the rotor and closely inspect the hole where it fits onto the shaft for any tell-tale darkened spots or carbon from arcing.

 

[bilbo1usa]

Re: 1960 75 hp Evinrude distributor/magneto question

Thanks Guys.
F_R, I read your reply on the other site, combined with what is here it is all very helpful.

Charlie, the rotor is old, has no grease and I suspect it's arcing. Short of replacing the cap on the distributor, it's the only thing I haven't replaced in the darn thing.
Thanks fellas, I'll log on with a status report, though it will take a couple of days to get a new rotor for that motor.

Bill

 

[Joe Reeves]

Re: 1960 75 hp Evinrude distributor/magneto question

A common failure is to have the rotor short out to the shaft upon which it is attached.

Points, on high lobe, should be set so that a .020 will pass thru but a .022 will not.

I assume that the small tapered spring and carbon brush is in the hole in the distributor cap... brush sits upon rotor.

KISS Method: Points open, coil fires to dist cap spring leading within cap to dist carbon brush, brush being upon rotor fires to whatever brass plug wire contact rotor is pointed to. No need to over complicate the simple magneto design with technical jargon.

No, Boobie wasn't being a smart alec. Outrageous goofs have been made by a great many intelligent people in the past.

NOTE: There are two (2) rotors for the older V4 models, one being for the magneto model, the other being for the automotive ignition model. They look similar BUT ARE NOT interchangeable.

Magneto rotor = 580260 (working end of rotor appears somewhat hook shaped)

Automotive rotor = 580338 (working end of rotor appears normally squared off)

 

[bilbo1usa]

Re: 1960 75 hp Evinrude distributor/magneto question

Outrageous goofs have been made by a great many intelligent people in the past.

Man, that could not be more true.

No, Boobie wasn't being a smart alec.

I hope that didn't come off badly, it was meant to be a jab in the ribs, not a punch in the gut.

So here is where I stand;
I bought a new rotor. Still no spark.
So I back tracked and tried to get the coil to shoot a spark from the Hi voltage button, by connecting a wire to the distributor case and holding it a bit off of the coil button.

No spark.

I used a drill to spin the magneto shaft to try to encourage the coil to make a spark.

Nothing.

I now have 2 coils. My old one, I thought might be bad, and one used one I bought off of a guy for a few bucks. He said he put it on a stevens meter and it tested good, and threw a spark.

Using a standard multi meter I get a reading from the coil hi output. I get the same reading at the carbon post that hits the rotor, when the coil is patched to the spring on the dist cap that touches it.
When I assemble the mess and test the spark plug wire output, there is almost nothing.

It seems I may have 2 issues: a weak coil and a loss of current from the rotor to the posts in the cap.

As Boobie suggested, I went through the whole thing and checked the wiring to be sure everything was well connected.

Thoughts?

Are there troubleshooting methods to assess the health of each component I haven't thought of?

Thanks all,
Bill

 

[boobie]

Re: 1960 75 hp Evinrude distributor/magneto question

This is the "smart alec" LOL. Have you put a new condensor in it ? Are the points clean and adjustusted properly ? When that mag is set up properly you can have it on the bench with the dist cap off and a spark tester hooked to the coil output, spin it over by hand and it should jump a 7/16" air gap. I've done it. That was a good mag. Normally a 1/4" gap is required. Sorry, I just read your first post again about the condensor replacement but you could have a bad new one. It's happened to me. Also, that second coil that you have could also be bad. All depends on how it was tested.

 

[CharlieB]

Re: 1960 75 hp Evinrude distributor/magneto question

"Drag' a clean piece of paper thru the points to ensure they are clean.

 

[F_R]

Re: 1960 75 hp Evinrude distributor/magneto question

Man, that could not be more true.

I hope that didn't come off badly, it was meant to be a jab in the ribs, not a punch in the gut.

So here is where I stand;
I bought a new rotor. Still no spark.
So I back tracked and tried to get the coil to shoot a spark from the Hi voltage button, by connecting a wire to the distributor case and holding it a bit off of the coil button.

No spark.

I used a drill to spin the magneto shaft to try to encourage the coil to make a spark.

Nothing.

I now have 2 coils. My old one, I thought might be bad, and one used one I bought off of a guy for a few bucks. He said he put it on a stevens meter and it tested good, and threw a spark.

Using a standard multi meter I get a reading from the coil hi output. I get the same reading at the carbon post that hits the rotor, when the coil is patched to the spring on the dist cap that touches it.
When I assemble the mess and test the spark plug wire output, there is almost nothing.

It seems I may have 2 issues: a weak coil and a loss of current from the rotor to the posts in the cap.

As Boobie suggested, I went through the whole thing and checked the wiring to be sure everything was well connected.

Thoughts?

Are there troubleshooting methods to assess the health of each component I haven't thought of?

Thanks all,
Bill

I suppose the mag is off the motor OR if on the motor the key is turned on, right? Better yet, disconnect the kill wire from the mag. Sorry, I had to ask such a dumb question.

As somebody said, you don't have to spin it fast to get a spark. In fact, I test them by sticking a pointy tool (center punch) in one of the holes in the pulley and rotate it by hand. That's only around 60 RPM.

I predict the chances are about 95% you have dirty or mis-adjusted breaker points. Another 4% says a bad connection at the stud which goes through the housing, connecting the coil to the points. Take that apart and polish everything up, shiny bright. Make sure that stud is NOT grounded to the case.

Next, take the points apart and polish each contact individually, again shiny bright. Make sure there is NO oil or anything on them (fingerprints or grit). When assembling the points back to the motor, make sure the spring is making good clean contact with the post on the breaker base. Make sure the little brass clip is present. Adjust the gap to .020" at their widest opening.

That magneto is simple and reliable, used for a number of years. I'd hate to say how many I've worked on. Gotta be over a thousand.

You cannot test spark with an ordinary multimeter. Probably even blow your meter. You are talking about around 40,000 volts in a spark on that magneto. Use the air gap method as I said earlier. And don't even mess with the distributor portion until you get spark at the coil. First things first.

 

[bilbo1usa]

Re: 1960 75 hp Evinrude distributor/magneto question

The mag is off the motor, and clamped in my vise.

The points are brand new, shiny and clean. Just as a precaution against the grease or fingerprints (I have oily skin) I cleaned the points with alcohol. I set them at .020, and have them opening at the high lobe on the cam. In fact, the cam has a mark where the point should be open (that was helpful!). Brass clips are on.

The kill switch wire has been totally removed from the mag.

The stud is definitely grounded to the case. This may be my issue.

Regarding the stud that goes through the case; this has me curious. If I test that stud for resistance against the case I get none...To me this means the stud is grounding to the case. I know this stud should be insulated from the case by the fiber washers.

But with the ground wire from the coil grounded to the case, even if I totally remove the primary wire from the stud and test for resistance to the case, with the wire touching nothing but air, I still get no resistance.

In other words, why is it that the stud is isolated from the case if the coil is grounded to the case anyway? And does this mean something is wrong at the most basic level with my mag and the primary wire to the points is acting like a kill switch?
How can I get the primary wire from the coil to return full resistance to the case when the other wire from the coil is grounded to the case?

Sorry guys, I really appreciate your help with this issue.
Bill

 

[Joe Reeves]

Re: 1960 75 hp Evinrude distributor/magneto question

The connection stud at the side of the magneto is totally insulated from the magneto case.... at least it better be. It is simply a connection point between the points assembly and the ignition coil. Also has a kill wire attached to it when assembled on the engine that leads to one of the ignition switch "M" terminals, with the other "M" terminal connected to ground.

Wires leading from the coil.... one is longer than the other. Short one connects to one of the coil retaining screws. The other longer one connects to that insulated stud along with the wire leading from the points assembly.

The internal wiring of the coil should have continuity as follows:

(Regular Magneto Coils - Continuity Test)
(J. Reeves)

Checking the continuity of the ignition coils....... Have the ohm meter set to High Ohms.

Remove the primary wire from that insulated stud. Remove the coil ground wire. You do not want either of these wires touching anything.

Connect the black lead of a ohm meter to the coil button terminal, then with the red ohm meter lead, touch the ground wire of the coil.

Then touch (still with the red lead) the primary wire. You should get a reading on both touches (contacts), one reading lower than the other. If not, consider the coil faulty. Poor or no continuity of a coil (or plug wire) is one reason for weak spark, s/plug fouling, or no spark.

Looking straight down at the magneto pulley, I'm sure that you know the pulley must rotate clockwise but I felt this would be worth mentioning.

Where, approximately, are you located?

 

[bilbo1usa]

Re: 1960 75 hp Evinrude distributor/magneto question

Thanks Joe
I'm in San Diego, CA. Understood on the clockwise rotation.
I'll do the tests on my coil(s) just as you have described when I get home from work, and post the results.

Like F_R said in his last post; this is a simple and reliable system. That's why I'm getting the feeling I'm overlooking something obvious, like a grounding issue.

Thanks for your time and the info.
Bill

 

[Joe Reeves]

Re: 1960 75 hp Evinrude distributor/magneto question

One thing I neglected to mention..... I'm sure you've noticed that the armature coil laminates are many plates stacked on top of one another if you've looked in that area. Obviously they must be in perfect alignment. I have seen a couple of those armatures where somehow that stack is disrupted and moves some of those plates out of place. When this happens, the magnetic flux is disrupted.... no spark.

Just another one of those things I thought worth mentioning

You're too far away.... I was going to tell you to run that thing over here and I'd give you a hand.

 

[bilbo1usa]

Re: 1960 75 hp Evinrude distributor/magneto question

You're too far away.... I was going to tell you to run that thing over here and I'd give you a hand.

Heh, yeah, that's a long tow. You're a good man, thanks for offering.

Well I tested my 1st coil, and it gave a reading of 006 ohms on both wires from the coil.
the 'new' coil I bought that had been 'tested' gave no reading.

As far as the plates your speaking of...do you mean the stack of plates that are spinning on the shaft between the two magnets?
If so, there might be an issue there as well. When I 1st opened this thing up, after poor performance on the water, I replaced the points and condensor. I opened up the distributor cap, and cleaned the rotor, but didn't give it a very detailed look. So I closed it up and tried to test the new points.

When it gave no spark I decided to open up the cap and give a detailed look, and I found pieces of the spring that rests on the coil button down in the magneto area (the tip of spring had shattered), and a piece of the spring had dislodged one of the plates during the usual spinning of the magneto when I tried to test my 'repair'. I was able to straighten it out and realign the plate with the other plates, but after that, no spark.
I was able to stretch the spring down enough that it makes good contact with the button again.

Geez maybe I should look for a new distributor. Just didn't want to dump a lot of $$ into this thing (more than I already have).
Thanks,
Bill

 

[F_R]

Re: 1960 75 hp Evinrude distributor/magneto question

Resistance between the coil's ground wire and the points wire should be around one ohm. Resistance between the spark button and ground wire should be several k-ohms. Exact figures are not to worry about, if you are in the ballpark, you are ok. I don't know where you got the funky 006 ohm reading.

EDIT: Now hold on just a minute here. You wrote:
As far as the plates your speaking of...do you mean the stack of plates that are spinning on the shaft between the two magnets?
If so, there might be an issue there as well. When I 1st opened this thing up, after poor performance on the water, I replaced the points and condensor. I opened up the distributor cap, and cleaned the rotor, but didn't give it a very detailed look. So I closed it up and tried to test the new points.

When it gave no spark I decided to open up the cap and give a detailed look, and I found pieces of the spring that rests on the coil button down in the magneto area (the tip of spring had shattered), and a piece of the spring had dislodged one of the plates during the usual spinning of the magneto when I tried to test my 'repair'. I was able to straighten it out and realign the plate with the other plates, but after that, no spark.
I was able to stretch the spring down enough that it makes good contact with the button again.

Is there any possibility that the shaft has rotated in the stack of plates? I've never heard of that happening, but if it did happen, you certanly wouldn't have any spark. The timing of those plates in relation to the points' opening time is critical. Just a little bit off would kill it. Like I say, that would be a new one on me. Something I never would have guessed.

 

[bilbo1usa]

Re: 1960 75 hp Evinrude distributor/magneto question

Yes I guess anything's possible! I can take a good look at the shaft and it's alignment to the plates and see. I like you would be suprised if it happened, but stranger things have happened before.

If the shaft didn't spin in the plates, do you think dislodging one of the plates and pushing it back in would have affected the performance to a degree that there would be no spark?

How critical is the lamination (greenish color) that is painted over the plates? It was definitely scraped off of the edges of the plates in a few spots. I'll try to put a few pictures on here tomorrow, or later tonight.

Thanks F_R

Bill

 

[F_R]

Re: 1960 75 hp Evinrude distributor/magneto question

I don't think one plate would matter as long as you got it back to where it belongs. As for the green coating, without getting overly technical again, it is to prevent the plates from touching each other, which would make them magnetically act as one big hunk of metal. Eddy currents is the tech term if you want to impress somebody. Minor damage won't hurt it.