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1990 Evinrude 70 problems...

B

badtomatoes

Member
Took my new (to me) boat out for the second time today. The engine started right up, though it did run quite smoky for a few minutes. Took it out and it seemed to run "okay" but seems great at full throttle. Ran about 2-3 miles, shut it down to fish for about 20 minutes. She started instantly with a touch of the key, then died flat, seemed like an electical or ignition type of failure because when it would die, it would do it immediately. Tried to stary with no luck for about 20 minutes. Finally got it going again and it seemed that I would have to start it, let it idle for a minute or two, only then would I get into the throttle. Maybe it was just paranoia and/or fear, but that's how I kept it going. It did the start the die thing once or twice again after, usually when I would put it into gear. If I tried to re-crank from the ignition "on" position, it just cranked with no fire. When I would first turn the ignition switch to the off position before cranking, it seemed to want to fire. Could be overthinking this part though. The engine seems to have an okay, though not great idle quality, but i dont know how smooth I should expect from a 1990 2 stroke engine. When I am accelerating at part throttle, the engine seems to run rough, almost like it is "loading up", not quite sure if it's a miss. When it's fully open, the engine is smooth and strong. Does this sound like a familiar problem to anyone?

Part of my issue is just not knowing what is "normal" or characteristic operation. I dont know if what I think might be rough or poor running might be considered acceptable for a 20 plus year old outboard.

Im an automotive guy and have all the tools I might need. From here I pan to do a few things. Please critique my game plan if you feel the need:

Replace the NGK with the factory recommended plugs (I think Champion) and inspect for irregularities.
Visually inspect all ignition components
Check resistance of ignition coils, charge coil, sensor coil
Perform compression test

After that- sync and link?
Carb rebuilds?

Thanks in advance for any helpful feedback!
 
Compression test should be step #1 on this motor.----If you get spark that jumps a gap of 7/16" on all 3 then you have done a test of all ignition components.
 
No dispute that the engine needs a strong spark, but it needs to be consistent and at the right time as well. My issues with this engine seem to come and go, leading me to think I have an intermittent electrical issue. The mid-range throttle/RPM seems to be a bit rough consistently, which may or may not be related. I'm going to do as many of the tests as I can tonight and report back with my findings.

Thanks for the input racerone.
 
Your ignition system is very good and well engineered !------Unless the flywheel key is sheared the timing will be spot on .----That is if no one has tampered with it.-------Does the hose for the tell tale come off the side of the block or off the top of the block ??
 
The fuel has been in the tank for only a week or so.

Didn't have time to do any of the tests on the engine last night. The hose for the tell tale comes out of the port side of the block near the bottom.

What does that tell you about this engine?

Thanks again.
 
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There was a service bulletin put out by the factory in 1994 to move that hose to the top of the block.----To me that means that the motor has not been looked at by a caring / knowledgeable shop or mechanic !!!
 
Update:
Compression is an even 100 across the board. The plugs are slightly wet from unburned fuel. All 3 look about the same.

I was watching the Hawks game last night- too tired to check compression then but got my DVOM to check resistance of the rectifier and stator.

I got 1.9 ohms for the stator. Spec is 1.4 ohms plus or minus 0.1.

Also checked the rectifier resistance . Numbers below.
Used a Fluke 87 DVOM for all measurements. Checked each connection with ohmmeter in both polarities.

YEL/GRY to Ground= OL/255k ohms
YEL to Ground= OL/240k ohms
RED to YEL/GRY= 238k/1.8M ohms
RED to YEL= 230k/1.5M ohms

While I can see a definite pattern amongst the connections, these don't jive with what I would expect to see. As I've seen with diodes elsewhere, resistance is infinite (OL) in one direction, and very low in the other. The manual also states this without giving a spec. It just says results should be similar. Results are similar- just not what was expected.

I know it's a fat chance, but is there anyone who could take some readings off of their 3 cylinder for me to compare to? Rectifier is cheap enough, but I want to find the problem, not change parts. Spark test coming next...
 
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The compression you mentioned "across the board" is suitable, preferably slightly higher but okay. Double check it from time to time to see if the readings change.

If a "spark test" has been made, I have apparently overlooked it, hence this post................

NOTE:...... The spark test must be made with the spark plugs removed in order to obtain the highest test rpm available. The cranking rpm must be at least 300 rpm in order for the stator to energize the powerpack (Keeping it simple).

The test is to be made using a spark tester whereas a gap can be set to 7/16" on that model for the spark to jump. The spark, on all cylinders, should be a strong wide blue lightning like flame bridging that gap, a real SNAP! Is it?

If it is... Stop trouble shooting the ignition system with the following exception and reasoning.

The "stator" under the flywheel is the beginning of both the battery charging system and the ignition system. A series of small coils providing AC voltage to the rectifier... and on that model, three larger coils that provide approximately 300 AC volts to the powerpack capacitor, needed in order to energize the pack.

Some of these stators will fail in a manner whereas they overheat, crack, and drip a sticky looking substance down upon the timer base and powerhead area... in the process of failing. Normally, when this failing starts, the stator will function perfectly... the test instruments register normal readings, the ignition functions, the engine starts and runs as it should, and all is well... BUT... as the stator heats up, a voltage drop from the stator to the powerpack takes place and the ignition becomes weak, erratic, and eventually fails alltogether.

Case in point (cracked leaking stator).... Cold engine starts and runs fine letting one get to a good fishing area, engine shuts down and one fishes for thirty minutes or so. While fishing for those thirty minutes, all of that engine heat is rising and settling right at the stator under the flywheel (and if faulty) resuting in the mentioned voltage drop to the powerpack.

This may not be your problem BUT a close visual inspection should be made of that stator to eliminate that possibility.

If the stator checks out visually and meter wise, you have the strong spark that jumps the 7/16" gap, and compression is as it should be... move your trouble shooting on to the fuel section.

(Spark Tester - Home Made)
(J. Reeves)

You can use a medium size philips screwdriver (#2 I believe) inserted into the spark plug boot spring connector, then hold the screwdriver shank approximately 7/16" away from the block to check the spark or build the following:

A spark tester can be made with a piece of 1x4 or 1x6, drive a few finishing nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere. Use small alligator clips on the other end of the wires to connect to ground and to the spark plug connector that exists inside of the rubber plug boot.


Using the above, one could easily build a spark tester whereas they could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:




..........X1..........X2


.................X..(grd)


..........X3..........X4

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

http://shop.ebay.com/Joe_OMC32/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
 
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I find no traces of melted sticky looking anything under the flywheel at/near or under the stator.

The only thing that bothers me is the stator resistance. I got a reading of 1.9 ohms, whereas the specification is 1.4 plus or minus 0.1. I dont know how crucial the resistance is. I work on cars all day, and often the resistance numbers are off a little on perfectly good parts. Any thoughts on this? If I'm to go by the book, that would mean the stator is bad....

Anyway, spark looks good and strong on all three.

On the the fuel system...???....
 
My meter is a Fluke 87 v.

It has a peak voltage setting on it, might just give it a try to see what I find. Worst case, I bring my oscilloscope home and check it out.
 
Warning! I might be over-thinking things again...

The voltage gauge on the dash was showing 12v while the engine was running- making me think there is a charging issue. The system voltage on my sonar unit agreed with the voltage gauge on the dash. Considering the stator and rectifier are tied in to both charging and ignition systems, I definitely need to do some peak voltage testing.

While anything is possible, my gut is telling me this is an electrical issue rather than fuel. Based on the condition of the plugs ( all in similar condition and kind of wet), I believe this issue is something common to all three cylinders.

I get aggravated when I don't quickly find the source of the problem I am troubleshooting, but it sure is gratifying once its fixed!

I'll keep plugging away and let you all know what I find.
Thanks again!
 
No dice with my meter for the peak voltage readings . Took a few resistance measurements at the amphenol connectors, most of which were normal.

The charge coil resistance came out to 396 ohms. Spec is 480 plus or minus 25

I am thinking a new stator might be in order. I hate to do so without knowing for sure. I guess I can't argue with an ohmmeter though....
 
UPDATES:

So I finally brought my scope home and had enough energy to hook it up tonight. Double checked resistance between terminals A and B on the stator and got 401 ohms- basically the same as my Fluke. Also used the scope to measure peak voltage from both terminal A and B to ground. The factory service manual states that if there is any measurable voltage present, the stator is shorted and needs to be replaced. Can't remember the exact number I got, but I did find voltage present on each. Going to be buying a stator unfortunately.

ANOTHER ISSUE?
The outer plastic bushing on the throttle cam follower is cracked and mostly falling off. I could see how sometimes there would be a longer than delay in throttle opening with this little piece broken. Could this explain the part throttle hesitation I've been noticing?

Thanks for any and all help!
 
What I found using my scope from on of the charge coil leads to ground. The other lead had a similar pattern.
image.jpg
The broken collar or roller is seen below...
 

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The throttle roller cam breaking away would indeed lead to a hesitation problem as throttle is applied.

When this non starting problem takes place, have you ever removed the spark plugs and performed a 7/16" spark test? If not, that would tell the tale.

With the non starting problem present, if the result was either a weak spark or a non existent spark, then obviously the problem is an ignition one.

This could be a failing stator as you obviously suspect... OR... a intermittent short within the ignition switch or wiring harness (Normally the switch).

The igniiton switch voltage has been known to short out internally to the "M" terminal that the Black/Yellow wire (kill circuit to powerpack) attaches to. To test the switch, simply disconnect the black/yellow wire from that "M" terminal, turn the ignition key to the ON/RUN position (engine NOT running), then with a volt meter set to a setting whereas it would register even a microvolt... connect the meter leads between that "M" terminal and a good known ground.

If even a microvolt registers, replace the ignition switch. If no voltage exists... the switch checks out okay, that would lead me to suspect (as you do) the stator.
 
Joereeves-
Thanks once again for your input. I have not yet had a chance to test for spark when the issue occurs. I don't want to replace unnecessary parts, so I think I will hold off on the stator until (or unless) I can get the problem to happen again and test for spark at that time. I will be on a smaller lake this weekend where I should be able to get away with it safely. I'm going to test the ignition switch as you described. I'll let you all know what I find.
 
Just got home from a couple days fishing in Wisconsin. I had more time to mess with it and more fully understand what it's doing.

First- I replaced the throttle roller. The engine seems to idle a little higher in neutral now- @1000-1100.

The engine did die a few times. Sometimes it would only want to run well with the throttle open pretty far and at high RPMs. Other times it seemed that it would run well at 2500 and under. Following Joereeves' advice on starting, I never had too much trouble getting it to start, though some times it would die when I would give it some throttle when in gear. No real pattern of the weirdness here- sometimes it did it hot, sometimes cold.

Another thing I noticed: the engine is not charging the battery. The battery is brand new, and the connections are clean and tight. I thought I noticed this last time but wasn't sure. This weekend confirmed it for me. The voltmeter on the dash started at 13v on the first morning, it was down to 12 at the end of the day, and just below 12 the next morning. I hooked up a battery charger when we had a break, and the voltmeter read higher when running it the next time. My sonar unit shows the same voltage that appears on the guage, ruling out a goofy gauge.

i would like to think that these might be related but don't know for sure. I have a replacement CDI rectifier in hand. I am going to install and see about the charging issue. If it is still not charging, this would indicate a bad stator, right?

Thanks again everyone. Learning a lot here!
 
I had similar problem ended up being a broken wire that went to the magnito on the ignition switch, the wire was pinched from a zip tie under the steering colum
 
Got some more on the water time with this thing.

To clarify the issues- it intermittently runs rough and the engine seems to miss. Sometimes when this happens, I'll "play" with the throttle, either opening or closing it some more and it will clear up. Another time, it really only wanted to be at about 2000 rpm. A couple times the engine died on the water, but was able to restart it right away.

At this point my head is spinning and I'm not sure what to do. I guess I'll have to bite the bullet and ge a DVA tester since I don't know how to interpret the results from my scope... not sure if I should use total voltage (from peak to peak) or just simply the peak voltage. I was pretty sure the stator was bad but after doing more reading, it appears that many people had similar "missing" issues with a bad power pack. I don't want to throw parts at this thing... Can't afford to anyway. Was planning to take a fuel sample tomorrow and check for voltage coming from the ignition switch as Joereeves described.

Another question for everyone/anyone- how smooth (or rough) should this engine idle? It seems like she idles kind of rough, but not sure what is considered normal for one of these.

Thanks again!
 
Another update after scope testing-

So I removed my head from you know where and got started with my scope to check for peak voltage (as in not peak to peak). Anyway,

The stator failed every test listed in the factory manual. Strangely, the CDI troubleshooting guide has numbers conflicting with the factory manual. By the CDI guidelines, the peak voltage I got (170V) from the stator terminal A to B was okay. The factory manual said it should be at least 250V. There was also a test to see if the stator was grounded by testing for voltage from both terminal A and B to ground. I got 6V on terminal A, and 8V on terminal B. All tests further imply the stator is toast.

Joereeves- to follow up on your recommendation, I tested for voltage on the black/yellow wire. Sure enough, the voltage peaked at 0.012V (12 mV) and stabilized at 0.002 with the key in the "on" position. Does this conclusively mean the ignition switch is bad?


Thanks!
 
One last thought- where should I get an ignition switch?

Edit: Nevermind. I see I can buy one from this very site. Thanks!
 
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