Logo
FULL SITE MENU

1976 35 HP ignition problem

S

sparky72

New member
My model #35653G Evinrude has been acting up since I purchased it in July. Ran great for 10 minutes or so then starts missing and one cyl. drops out. The problem always follows the same ignition coil so I installed 2 new ones and it wouldn't run at all. I then had new points and condensors professionally installed with the original old coils on and it is doing the same thing. The one old ignition coil that does throw a spark reads about 12,000 ohms and the 2 new ones that don't seem to throw any spark read around 4500 ohms. Do I have a weak diver coil?
 
Very interesting, and I must admit I don't have an answer. Except those coil resistance readings sound suspect. The book says 13,500 ohms, plus or minus 1500. So that indicates your 12,000 is within the low end of the acceptable range, plus that is the one that works. I don't know what to tell you about the low 4500 ohms on the new ones. Sounds like you got the wrong coils (????)
 
They're the Sierra brand from Marine Engine. I guess I should try the Johnson Evinrude coil. Do you know what the voltage should be before the ignition coil? That should be pretty easy to test.
 
Not as easy to test as you might think. They work from an inductive kick from the driver coil when the points open. That kick is very fast and temporary. You would need a peak-reading voltmeter (DVA) to catch it. I don't have the slightest idea what the voltage reading would be. The CDI troubleshooting website may say, but I haven't looked.
 
I think your new coils will only work with the new exciter coil, or as Gator calls the "driver". The higher the number in ohms, the less continuity of course. Your new coils work with about 3x less resistance, so your exciter (driver), especially since it is likely weak, will not fire the coils with less resistance. Since your other parts have been professionally replaced, I strongly suspect the "driver". I have seen them fail with age before. You can go to CDI electronics on line diagnostics manual and look up the dva output volts for your "driver". The resistance of the "driver" may not give you an accurate answer. Properly diagnosed, the "driver" must produce the minimum listed voltage.....when cranking the motor at starting rpm's. This voltage comes, or course, in very minute pulses which are not detectable without a dva meter, or an attachment used with your own multimeter. This attachment retains the "pulse" and records the highest value for you to get a reading. These units are very helpful with any diagnosis of capacitor discharge ignition, primarily used in marine applications. The output voltage also is dependent on how strong the magnets are on your flywheel. So in rare occasions, the "driver" is okay, but the magnets are weak.
 
Last edited:
Another note, "drivers" output may vary depending on temperature of the coil itself, as well as the condition of the wires where they are flexing when the stator plate moves through its operation range. So the "driver" may give you intermittent or disturbing readings based on stator position, and temperature. In newer outboards only the trigger.....or timing coil is moving through throttle positions. This eliminates the constant wear on the wires to the stator or "driver coil". A trigger is commonly tested using ohms, but many techs/mechanics make the mistake by not testing the trigger through full operating range of the throttle. So, if the wires are damaged running to your "driver coil"......you can check that with the ohms scale while leaving the multimeter connected while moving the throttle from idle position to full throttle (WOT). I used to run into a similar problem with early GM electronic distributors starting in 1975. The pickup coil is constantly moving based on the vacuum acutated stator plate. In cold weather, the 2 wires going to that donut shaped coil, will crack and eventually deteriorate one conductor after the other, until the module looses its signal from the "trigger" (donut) coil. Then no spark. If outboards are used in very cold conditions, like Northern MN, say in late fall and early winter, the aforementioned scenario can be a critical consideration when diagnosing intermittent spark issues. The same holds true for equipment used in high heat with direct sun. I notice more electrical wiring deterioration in Mercurys not perhaps only due to their black color, but the original composition of the wiring insulation.
Ps. I have a 1976 15 that a customer gave me. One cylinder, he said, drops out after a 5 or 10 minute run. Its still awaiting my diagnosis. May be the same problem you have.....let us know what you find. Thanks, Tim
 
Last edited:
Thank you for the input guys. Tim, I see your'e from Duluth. This motor I'm working on is on a pontoon at our cabin by McGregor. Since I already have these two new coils it probably makes the most sense to get the new Exciter coil to replace the current driver coil? Marine Engine sells two driver coils. One from CDI electronics and the other from Johnson Evinrude. Any idea if the one from CDI would be compatible with my 4500 ohm coils? Or am I better off contacting Sierra Marine for the proper driver coil? My other option was to order the Evinrude coil assuming it's resistance would measure 12 to 14 thousand ohms. Then I don't have to pull the flywheel again.
 
The CDI parts are exceptional and compatable with everything. Sierra is also good, I'm on the fence on that one. Yes MacGregor is a short drive, go there fairly often in the summer. My wife, Raquel makes dresses and we sell them at arts and crafts shows all over western MN. Detroit Lakes is one of our best sales. I think it would be prudent to just change the exciter/driver......one in the same. I am kinda surprised the shop that changed points and condenser didn't recommend you do that anyway.
 
Just double check that you have the correct coils for your motor, then order the "driver" for the same, of course. These coils changed impedance over the years, so we have to be careful to match the coils with the "driver". CDI diagnostic manual is free online. Check out the proper coil impedance for your 35. CDI will state if their coils will test different. The points would not likely cause a failure on just one cylinder particularly the same as before. Did you say that the shop put in "new" points and condenser?
 
Yes. New points and condensers. Sounds great. I will check with CDI and hopefully get a new driver coil to match the new ignition coils I already have. Thanks for all the help. Boat is kinda put away for the winter, not sure if I'll get the motor running until spring but at least I'm on the right track.
 
Yes its close to snow time here, probably won't get my boat out again either, unless we get a warm day in November. I have a 1985 30 hp up at the cabin in remote NW Ontario, that lost spark in one cylinder only, without warning while freighting down the lake. I had a good used power pack and tried that, but no resolve. I will repair in the springtime, (already ruled out the final coils). The problems gotta be under the flywheel. I will replace all coils with new CDI equipment. A few extra bucks spent when you plan a trip into the wilderness is good insurance. This electronic stuff, no matter how you care for it, can fail without much of a warning. It can turn a good day into a huge problem.
 
Back
Top