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Johnson 150 no spark

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Bastoe17

New member
(Beware, lengthy post)

New poster, here.

Bought a 20' Neptune with a '93 150 Johnson from a friend a year ago. Immediately had it serviced, everything looked fine. However, every time I would take it out (the few times I was able to), it always gave me cold start trouble. Once I finally got it started and it warmed up, it ran great and started great while warm on the water. One day while waiting to put it back on the trailer, it killed and wouldn't even attempt to fire/turn over/anything. Got it back home, it sat for a couple months, but when I finally tried cranking it, I at least got the starter to turn but no spark. Changed stator because it had black gook on it and underneath it. That wasn't the problem.

I've considered the possibility of the power pack/coils, but everything I'm reading says the boat starts to run bad when warm if it's the power pack. And it ran great when warm.

Any idea what I should check next? Could it be the starter not putting out enough juice? Bought a new battery with the boat, so that's barely a year old.

Appreciate any and all input.
 
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Personally I'd start by giving the battery a fresh charge. If the stator was bad then it wouldn't have been charging it, plus having to crank it a bunch to get it to start cold may have drained the battery.

Lots of guys on here that know these outboards really well, listen to their advise when they chime in.
 
The stator is the beginning of both the battery charging and ignition system. That black sticky goop you saw is the result of the two large black coils melting down from the extreme heat... those black coil;s supply approximately 300 AC volts to the powerpack's capacitor in order to energize the pack. Your tachometer may have been malfunctioning for quite some time... and if so, this is an indication that that the voltage regulator/rectifier has failed and needs to be replaced before it catches on fire (which is a sure thing!).

You didn't say what you found to be the reason that the engine wouldn't even crank over with the electric starter. Was the 20 ampere power fuse blown? If so, that's a indication of a dead short.

Now, that being said..... the engine must crank over at least 300 rpms in order for the ignition to function. The spark plugs must be removed in order to obtain the highest rpm possible. The spark should jump a 7/16" gap with a strong blue lightning like flame... a real SNAP! Does it? Note that the air gap of 7/16" is important.

NOTE... Power-packs do not come and go... warm, cool, hot, cold, whatever... when they fail, they stay that way, they are dead forever! The stator however when melting down, will normally function okay when cold BUT when hot will act up... erratic, weak, eventually no ignition as you found out.

Keep us informed.
 
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Tach definitely doesn't work - hasn't since I got it. If I'm not mistaken, the regulator may have been replaced when I had it serviced, but I would have to double check that.

As for the no crank problem, I never found an issue. It was the strangest thing, it killed while waiting to put it back on the trailer, wouldn't crank/turn over/spark, nothing. Sat for a couple months and when I had time to fool with it, starter was at least turning. This is when I discovered that I'm not getting spark to any cylinder. I haven't checked my gaps, I will be sure to do that. But I find it hard to believe that all of my plugs went bad at once.
 
Failure to crank over.... Of course you're aware that if in gear, the engine won't crank over... BUT... then there's the finicky Neutral Safety Switch... sometime one needs to jiggle the throttle handle to get that thing in the proper position when they need a slight adjustment.

No... Spark plugs do not ever all go bad at once.

The tachometer operates off of the rectifier. Do the following test when you get the engine to run to find which component is at fault the tachometer or the regulator/rectifier.

(Testing Tachometer With Water Cooled Regulator/Rectifier)
(J. Reeves)

A quick check is to simply plug in a another new tachometer as a piece of test equipment. If the new tach works properly and the old tach didn't, obviously the old tach is faulty.... but usually boaters don't carry around a spare tach (see below).

A faulty rectifier wouldn't damage the tachometer, the tachometer simply wouldn't work. This is due to the fact that the tachometer operates off of the charging system and the rectifier converts AC voltage to DC voltage, enabling the charging system. A faulty rectifier disables the charging system, and the tachometer simply doesn't register.

However.... those water cooled regulator/rectifiers that are used on the 35 ampere charging systems (and some others) bring into play a different type problem, and as you've probably found out, they are really a pain to troubleshoot via the proper procedure. There's an easier way.

The tachometer sending/receiving setup operates off of the gray wire at the tachometer. That same gray wire exists at the engine wiring harness which is connected to the engine electrical terminal strip. You'll see that there is a gray wire leading from the regulator/rectifier to that terminal strip, and that there is another gray wire attached to it. That other gray wire is the wire leading to the tachometer which is the one you're looking for.

NOTE: For the later models that DO NOT incorporate a wiring terminal strip, splicing into the "Yellow Wire" mentioned will be necessary.

Normally the Gray wire leading from the tachometer is attached at the terminal strip to another Gray wire which leads from the water cooled voltage regulator/rectifier...... remove the gray wire that leads to the tachometer. Now, find the two (2) yellow wires leading from the stator to that terminal strip. Hopefully one of them is either yellow/gray or is connected to a yellow/gray wire at the terminal strip. If so, connect the gray wire you removed previously to that yellow/gray terminal. Start the engine and check the tachometers operation, and if the tachometer operates as it should, then the regulator/rectifier is faulty and will require replacing. If the tachometer is still faulty, replace the tachometer.

If neither of the yellow wires from the stator is yellow/gray, and neither is attached to a yellow/gray wire, then attach that gray tachometer wire to either yellow stator wire, then the other yellow wire, checking the tachometer operation on both connections.

I've found this method to be a quick and efficient way of finding out which component is faulty.... the tachometer or the regulator/rectifier. It sounds drawn out but really only takes a very short time to run through. If the water cooled regulator/rectifier proves to be faulty, don't put off replacing it as they have been known to catch on fire with disastrous consequences.
 
Sorry for the delayed response.
I appreciate the in-depth directions on diagnosing my rectifier, but the problem comes in when you say “Do the following check when you get the engine to run”. I can’t figure out how to get the engine to run. Haha.

Like I was saying, I’m not getting spark to any cylinder and I know the stator wasn’t the problem. My next two guesses are power pack or possibly starter, but I don’t want to go buying both if you (or anyone) could suggest which is most likely the problem.
I’m leaning towards power pack. Is there a good way to test this or do you know of a company that might have a free return policy of the power pack if that isn’t the problem?
 
You say that the stator wasn't your problem, however take my word for it... it apparently didn't cure your problem BUT it was most definitely a BIG problem with both the ignition and the charging system. I'm surprised the mechanic didn't catch that just by its appearance.

Note my previous statement about the engine must crank over at least 300 rpm (fast) for the stator to energize the powerpack capacitor. A slow cranking engine will not produce any spark!

Test the ignition switch for a ground short by: Remove the black/yellow wire from the ignition switch. Test for spark (7/16" gap). If you have spark with that wire removed (kill circuit) but no spark with the wire connected, replace the switch.

You mention that your two guesses are the powerpack and the starter...... Why the starter??
 
Well couldn’t a weak starter be the cause of a slow cranking engine? That’s one reason I’m thinking starter. Plus I want to make absolute sure it’s engaging the flywheel.
Battery is only a year old and it’s a pretty good battery, so I don’t really think that’s the problem.

I’ll give that kill switch a try.
 
Bastoe17 said:
Well couldn’t a weak starter be the cause of a slow cranking engine? That’s one reason I’m thinking starter. Plus I want to make absolute sure it’s engaging the flywheel. Battery is only a year old and it’s a pretty good battery, so I don’t really think that’s the problem. I’ll give that kill switch a try.
Click to expand...

Yes, absolutely... as I've stated a few times, a slow cranking engine will produce no spark/ignition... BUT... you haven't actually said that your engine cranks over slow. If your engine cranks over slow, there's one good reason for no ignition/spark!
 
That ignition system supplies 12V from solenoid to eye in case of slow cranking then power coil takes over when it starts. You can check it(yell w/red stripe) and if below 11v while cranking check starter /cables /battery. You can test stator ohms/output and and if good replace pack and eye as a set.
 
Well, I’ve done it, boys! Finally narrowed it down to the culprit and fixed it. I know I said my battery was only a year old, but turns out it was shot to ****. Replaced battery, then got a clicking noise when trying to turn over.
Took Racersone’s advice and tore the starter down, cleaned it up, and decided to buy a new solenoid as well

Turns out, it did the trick!

Thanks for all the help, guys. Outside of a fuel leak around some of the carbs, I’ve still got a couple of small issues which I may need some advice on. Other than that, thanks again! She’s back up and running!

Will be back in touch soon. ��
 
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