25hp evinrude '78 no spark after warm.. help

[kbait]

I've got a 25hp electronic ignition '78 manual start Evinrude. Totally loses spark after about 10mn and comes back briefly, then no more for a long while. Definately a spark issue. No overheat (can grab cylinder head for a brief time-normal, and good telltale and newer waterpump and tstat). I first had this issue last week. I searched the threads here for great ideas, as always. So, I found a hair drier and made a spark tester and put her on the stand, pulled the flywheel. Checked ohms on sensor coil and found 39 (good). Heated it up good w/hair dryer and it stayed about the same. Did the same w/charge coil under flywheel and it stayed at about 580 ohms. All wires look fine and unobstructed. Replaced and torqued flywheel and then checked both drive coils and they were like 270 and fluxuated slightly w/heating and cooling off. I got continuity from the kill button when pressed, not when in run mode, so I assume that's good. Rubber on kill button is fine too and it operates normally when used. I then concluded I had a bad amplifier/power pack (I then heated that, and at one point lost all spark, but upon further warming it came back?), so I replaced it with one from a previously running/broken lower unit 35hp that had the same pp and it sparked normally from both wires (7/16"). Then lake tested to find the exact same exact problem (10mn fine, kill at idle, start again, kill right at open throttle for at least 1/2 hour (time it took my 3hp kicker to get me home). I am stumped. I assumed since the other ignition components didn't fail w/hairdryer heat (and they all got pretty hot) that it had to be the pp since that did seem to fail briefly upon heating. So I replaced the powerpack. I spent a little more and got a new bombardier pp, as I assume it'd be best quality. Exact same result. I am confident I'm getting no spark at all upon failure, and I'm POSITIVE it's not a fuel or overheat issue, and I have 115psi on both cyls. When it will start after a fail, it's as if there was never a problem(till next fail-quickly) When it dies under power, it's not even a sputter - it's like you pressed the kill button. Immediate. I definately don't want to throw $ at another powerpack as I don't want to believe they all failed the same, especially the new one. I thought I did my homework to eliminate stuff and ID the problem. I have inspected all wires, checked and cleaned the 3 ground's I found, and I am at a loss. Could I have spent $$ on a new, junk pp? If any of you fine folks have had a similar head scratcher, I'd sure appreciate any advice. I'm thinking of putting 2 new drive coils in, but I assume they wouldn't just happen to fail at the exact same time every time she fails. Am I right about this? Could one failing coil leave no spark at all? Since they're both downstream of the pp I can't see how. I understand point setups, but this electronic ignition issue has me baffled. I am quite sure that the spark on both cyl's totally dies all at once and totally upon each failure. Thanks for any and all thoughts. kbait

 

[HighTrim]

Re: 25hp evinrude '78 no spark after warm.. help

Welcome to iboats. You are right in assuming it PROBABLY isnt the coils, unless both are failing. I would start by checking the stator. Heat it up with the hair dryer, and see if it dies, or get out your multimeter and you should read approximately 500 ohms from the brown wire to engine ground. Then check the DVA output from the stator. You should have a reading of at least 150V or more from the brown wire to engine ground (while connected to the pack).

 

[kbait]

Re: 25hp evinrude '78 no spark after warm.. help

Thanks for the quick reply HT. Mine is a manual start. This may be a dumb question, but does it have a stator windings under the plate? I figured it just has the charge coil and sensor coil (under flywheel), ppack and drive coils. I didn't see any windings under the 'stator' plate, or any wires to test in that area besides the charge and sensor coil leads. Thanks!

 

[HighTrim]

Re: 25hp evinrude '78 no spark after warm.. help

ah ok, sorry, I just assumed electric start for some reason. What is your model number on that motor?

 

[kbait]

Re: 25hp evinrude '78 no spark after warm.. help

25802c

 

[HighTrim]

Re: 25hp evinrude '78 no spark after warm.. help

Sounds like you have really covered your bases then. I would try testing the ignition coils though. Follow this advice by J Reeves.

It's a good idea to incorporate a continuity test of the coil windings as follows. A coil can be made to fire even with broken windings BUT it will let you down at the worse possible moment.

(Magneto Capacitance Discharge Coils - Continuity Test))
(J. Reeves)
Check the continuity of the ignition coils. Remove the primary orange wire from whatever it's connected to. It may be connected to a powerpack screw type terminal, a rubber plug connector, or it may simply plug onto a small boss terminal of the coil itself.

Connect the black lead of a ohm meter to the spark plug boot terminal, then with the red ohm meter lead, touch the ground of the coil or the powerhead itself if the coil is still installed.

Then touch (still with the red lead) the orange wire if it's attached to the coil, or if it's not attached, touch the primary stud of the coil. You should get a reading on both touches (contacts). If not, check the spring terminal inside the rubber boots of the spark plug wire.

 

[samo_ott]

Re: 25hp evinrude '78 no spark after warm.. help

Phew... am I glad that all 30+ of my engines have points and coils...

 

[kbait]

Re: 25hp evinrude '78 no spark after warm.. help

So I threw her on the bench again, used a spark tester and no spark. Tested sensor and charge coils again - good. Removed and checked drive (ignition) coils and they test good and look good w/no visible cracks. I cleaned all the grounds and inspected wires again. Now I have spark. Don't exactly know why. I then ran in test tank for one hour w/no problems, so I'll lake test it again and see if it fails again and post result. Thanks again

 

[HighTrim]

Re: 25hp evinrude '78 no spark after warm.. help

Good to hear. It always seems like 90 percent of the time the issue is wiring/connector related. Gotta make those connectors shine.

 

[CharlieB]

Re: 25hp evinrude '78 no spark after warm.. help

I'd almost be willing to bet that your problem was poor grounds of the coils under the flywheel, failing with thermal expansion of, or differing expansion rates of the coils and the engine causing poor grounds.

Light sanding of the mounting points should cure this for a long time, internal stainless star washers on mounting screws, and center punching a 'ring' of 'points' around the engine threaded holes so as to ensure a better contact 'bite' between the parts. Warning, do not use too large a hammer on the punch, small 'raises' is all that is needed, too large and the contact areas could conceivably elevate the coils, then eventual wearing of the raises could loosen the mounting screws.

 

[kbait]

Re: 25hp evinrude '78 no spark after warm.. help

Well, since last post she ran fine one day, and failed the next, requiring a 5 mile jaunt w/'52 3hp. (that one always works!). I put it on the bench today and hooked up the spark tester and nothing. I unplugged both powerpack plugs and again found correct readings on drive coils, sensor coil and charge coil. I still couldn't believe the powerpack failed that quickly, so I again checked for continuity from the plug lead of the kill switch to ground. It flashed for just a moment like there was a connection where there obviously shouldn't be, so I pulled the kill switch lead out of the pp socket, put it all together, and now I have spark (and a spare powerpack!). Thanks to all who posted! And, yes, I'll remember to DISABLE the kill switch to diagnose any possible powerpack problems I may encounter in the future Now that I've registered here, I'll take a peek at other's problems and try to pay it forward.