Johnson Stinger 75 hp. ignition problem

[Chuck B.]

I am a car, truck, and diesel mechanic, but never worked on boats before. I have purchased a boat with 75 hp. Stinger Johnson. The problem I have is the top and middle cylinders have no spark. Engine runs on bottom cylider only, Cant believe it cranks at all, but does. Was told by previous owner that power pack and the 2 coils were the culprits. Would like to check out fully before just adding parts. I dont do that to my customers or to myself. Also will sometimes shock you through key when shutting down. What triggers the coils to fire? What year motor is it so I can purchase a manual? Model# J75ERLCSA Ser# J5307419. Thank you for any help you can give me.

[jegervais]

Your 1980 model 75hp uses a CD ignition system. The operating voltage is generated by a charge coil which is part of the stator assembly under the flywheel. The charge coil typically develops 250 volts which is stored in a capacitor in the power pack. This model also incorporates a timer-base assembly which consists of 3 sets of sensor coils. These sensor coils control spark to each cylinder - a magnet which is epoxied to the center hub of the flywheel controls the firing of the sensor coils. A sensor coil typically puts out 3 to 5 volts. This low voltage is sent to the "gate" of a silicon controlled rectifier (SCR) in the powerpack and the SCR releases the voltage which is stored in the capacitor to the appropriate ignition coil to provide the spark for that cylinder.You'll need a peak-reading volt meter (or a DVA adapter to convert a digital vom to a peak reader). The charge coil wires are brown, the timer base probably has blue, purple and green (#1, 2, & 3 respectively) as well as a white "ground" wire. You should see around 250 volts between the brown leads and 3 to 5 volts between blue & white, purple & white and green & white.You would probably find a factory service manual quite helpful and it will also explain in greater detail the theory of operation. A factory service manual is available from any Evinrude dealer under part number 506773.-John

[omctech]

John is right. However, you must realize that everything coming out from underneath the flywheel is AC electricity. If a peak reading voltmeter is not available,set your meter to low volt scale when testing your sensor coil output and expect a reading above 1 volt. To test your coils, set your meter to high ohms scale, first test is between the small input terminal and ground, second is between small input and the output to the plug. Should read continuity both directions. Hope this helps.

[Chuck B.]

I take it that this powerpack is nothing like an ignition module on a vehicle. Usually when they go out, they wont spark at all. Is it possible for the powerpack to be bad and still allow spark on one cylinder? Just not used to thinking in this manner Will get my fluke out and check The other parts while I wait on the manual. Thanks for your help

[jegervais]

Chuck,That is correct. A power pack can cause the ignition to to loose spark on 1, 2 or all 3 cylinders - The same is true regarding the timer base. Since the charge coil supplies the operating voltage for all 3 cylinders, it would only be suspect in a complete "no spark" situation (only after eliminating the stop circuit as a possible cause). Having more than 1 ignition coil fail at the same time is an extremely rare event.-John

[Chuck B.]

Thanks John & omctech, you both have been very helpful. Thanks for spending your valuable time to answer my questions. Chuck B.