1972 85hp Johnson Starts at night Won't Start during day

[Jimbo's Jumbo]

My 1972 85hp Johnson will start and run normally at night (it will start very quickly when I try around 10pm every time on four different days), but during the day (I usually get around to trying it at about noon and it sits in a sunny spot) it has no spark at all. I bought a new battery, checked the amp with a multimeter (it's getting 12v to the terminal and is drawing 0.07amps when motor is not running), checked the coil with the multimeter and there is almost no resistance across the coils. I didn't pull the flywheel to check the points and breakers due to the fact it starts at night and would like to avoid this if possible (but will do it if needed).

During the day I pulled the plugs and checked for spark (and get none on all four), but when I check the spark at night it sparks on all four. The starter motor also works during the day, so the circuit for the starter to turn the flywheel is working properly both day and night. It's got me a bit stumped to say the least.

Any thoughts on this one? I thought it might be a wire that heats during the day causing it to pull apart a broken wire or something, but I'm not sure. I thought it might be something with the temp sensor, but it is only attached to the hot horn according to the wiring diagram in my repair manual. If anyone has an idea of what might be causing this, any help would be greatly appreciated.

 

[pn]

check your grounds and your kill switch.

 

[racerone]

Spark may be difficult to see in the daytime.---How are you checking for spark ?

 

[Tim Frank]

Any chance this is a "Made in Romania" Johnson? You could try hanging a clump of garlic on the steering connection.

Seriously though, sounds like an electrical component is getting too warm.
Try either getting it out of the sun and seeing if it will start, or get a can of freeze spray (electronics test stuff) and selectively blast
Check your manual and make a list of the items that have commonality to kill spark to ALL cylinders and check those first.

 

[Jimbo's Jumbo]

pn - I've checked most of the grounds and they seem ok, but I will go over those again for sure. I'm not sure there is a kill switch on this motor, it doesn't show one in the wiring diagram and there is not a dongle attachment on the control box.

racerone- I've been pulling the plugs and holding against the block with a pair of insulated pliers. It is tough, but I started using a cardboard box with a hole cut in it to make the plug dark enough to see the spark for sure.

Tim - LOL... .I'll give the garlic a try... can't make it any worse. Thanks for the trick, i'll check out this freeze spray stuff you are talking about. Where do you typically get some?


On a side note. I tried it this morning before the sun started hitting it around 9am and it started right up. But then after about an hour sitting in the sun, nothing once again. Could it be a malfunctioning thermo switch? I haven't read the entire manual yet, and I have not found anything on this switch other than in the wiring diagram and on the powerhead exploded view. There is no mention of it in the testing of the ignition system.

Thanks guys, hoping I can get this vampire motor going!!!!

 

[cobbcfi]

Is this a new issue? Was it starting during the heat of the day and it just suddenly stopped? Have you done any wiring work recently? What was the last thing you did before it stopped starting?

 

[Jimbo's Jumbo]

cobbcfi - it's a new issue. I am the third owner, and the previous two never had any issues with it. Had it out one weekend and no trouble, the next weekend the starter would not engage. I traced the problem to the starter safety switch which was remaining open due to a faulty switch. I got that working now, but then I had no spark at all, so I replaced the battery (it was time for a new one anyhow), and now it will only show spark during the cool of the day or night. I've yet to try early in the night, but i'd rather just find the problem causing the issue.
I'm really wondering what the Thermo Switch is responsible for. It looks like it is a switch that opens and closes based on temp, and it is attached to the switch and key assembly, so I'm thinking that might be the culprit, but I'm not sure. If I'm correct in it's location, I think it is potted into the head of the engine just behind the terminal on the top of the engine block. I'm not sure how to test it or even get it out of there if needed as I have not yet come across it in my repair manual.

 

[Joe Reeves]

Have you somehow offended the aging witch doctor Queen Angela of New Orleans by any chance? It sounds like you and your engine have both been deeply bestowed with the Night Crawlers Curse.

(Point Setting Of Battery Capacitance Discharge)
( Ignition Models - 1968 thru 1972)
(Some have points - Some do not)
(Joe Reeves)

The points must be set to .010 but no wider than .010..... BUT in some instances due to a possible slight inaccurately machined crankshaft lobe or a slight offset of one set of points, a setting slightly less than .010 would be required as follows.

Whether the crankshaft has two or three lobes, when setting the points, check the setting of the points on each individual lobe by rotating the crankshaft by hand.

You may find that setting one set of points to .010 on one lobe, then turning the crankshaft to the next lobe, the gap measures .011 or .012 (too wide). This is where you would need to close that gap down to the required .010. A gap too wide can result in a ignition miss when throttle is applied.

Bottom line, pertaining to the point setting at the various lobe locations____ .010, .010, .009, is okay____ .010, .010, .011 is not!
********************
(Voltage Drop To Battery Capacitance Discharge)
( Pulsepack When Electric Starter Is Engaged)
(J. Reeves)

On the older Battery Capacitance Discharge ignition systems (1968-1972), the electric starter reaches a point, even with a top notch battery, whereas the starter will draw excess voltage/current/whatever which results in a voltage drop to the pulsepack. The cure is to purchase a diode which is capable of handling 12 volts and installing it between the starter terminal of the starter solenoid (NOT the battery cable terminal) and the wiring terminal that supplies voltage to the pulsepack.

The diode must be installed so that the current flows from the starter terminal of the solenoid to the pulsepack... NOT vice versa. When that diode is installed in this manner, when the key is turned to the start position, the voltage that is applied to the starter is also applied directly to the pulsepack via the diode effectively eliminating the voltage drop and energizing the pulsepack with the required voltage needed for its proper operation.
********************
(Battery Capacitance Dischage Powerpack Test)
Various OMC Engines - 1968 to 1972)
(J. Reeves)
Purchase a small 12v bulb at your local automotive parts store (the 12v bulb is to look like a flashlight bulb, not a headlight bulb). Solder two wires to that bulb, one to the side of the bulb (ground), and the other to the positive point. You might use a bulb of a somewhat lower voltage to obtain a brighter glow... just a suggestion.

Remove the spark plugs. With the key in the on position, make sure that you have 12v going to the pack at the terminal block (purple wire). Now, connect the ground wire from the bulb to any powerhead ground. Connect the wire from the positive point of that bulb to the powerpack wire that is connected to the coil wire on the terminal board (blue wire).

Crank the engine and observe that bulb closely (CLOSELY!). If that bulb glows even the slightest bit, the powerpack is okay. It may be a very dim glow... just so it glows! If it doesn't glow, the pack has failed.

Keep in mind, that type powerpack (Battery Capacitance Discharge) demands a top notch battery of at least 70 amp hours. Any less will, in time, cause powerpack failure.

 

[Jimbo's Jumbo]

Joe - I've never been to Louisiana, so I don't think so... but my girlfriend is from the south so maybe there's something to that one too :witless:

The voltage drop due to the starter motor running is very interesting. I think I'll put in a diode just to protect the amplifier from premature failure due to voltage drop across it's terminals. And it might be part of the problem with what I'm dealing with too. Where do you get a 12v dc current diode? Do I have to splice it in (such as soldering it into place or crimp style connectors) or can I get one with terminal connection ends that I can wire to the terminal screw connections?

I still may have to pull the flywheel and check the points, but I'm really trying to avoid that until last thing. Still wondering about what the manual calls the Thermo Switch, which is apparently different from the Temp Switch which causes the hot horn to sound. If this was not functioning properly I think it might cause the issue, but I'm not sure. Will try to dig into it a bit more this week sometime and figure out if that is the issue, but I would really like to get a diode and protect that amp, so if you have any leads on where to get a good one, I'd love to not have to search.

Thanks guys, great info thus far, keep the ideas coming. I'll definitely post the results when I get her going.

 

[Joe Reeves]

The point setting is pretty critical I've found... even having one open up to .011 has created problems.

Be sure to torque that flyewheel nut to 105 foot pounds when re-installing to avoid a sheared flywheel key.

Most diodes do not come with terminal ends, and usually the leads need to be lengthened. It's best to go to the trouble to solder whatever needs to be connected (terminals, etc) and also heat shrink tubing where needed. Radio Shack or any electronic supply store would have the diode.

 

[boobie]

A wild guess would be a bad power pack.

 

[cobbcfi]

I have a question, I work for a major aerospace manufacturer in South Carolina (a no brainer there) and I work within tolerances of .001, and that's one thousandth of an inch, and on occasion it can and will come down to a few one-ten thousandths of an inch.. Were are talking a fraction of the width of a hair.. You are talking about .010 or one-hundredth of an inch and then all of a sudden the .012, that's twelve-thousandths of an inch can make or break the deal?? This is only a thought and not a callous remark by any means, I just didn't know that outboard motors had these kind of tolerances. I am more intrigued than ever before..

 

[Tim Frank]

Tolerances of +/- 0.001" are nothing special.
There are many tolerances on an outboard that plus or minus a couple of "thou".
In this case it is an electrical issue that relates directly to timing.

 

[Joe Reeves]

I have a question, I work for a major aerospace manufacturer in South Carolina (a no brainer there) and I work within tolerances of .001, and that's one thousandth of an inch, and on occasion it can and will come down to a few one-ten thousandths of an inch.. Were are talking a fraction of the width of a hair.. You are talking about .010 or one-hundredth of an inch and then all of a sudden the .012, that's twelve-thousandths of an inch can make or break the deal?? This is only a thought and not a callous remark by any means, I just didn't know that outboard motors had these kind of tolerances. I am more intrigued than ever before..

Your reasoning is understood, however, having been associated with OMC (Outboard Marine Corporation) from 1960 to retirement in 1991, I have encountered and discovered more than my share of weird problems and cures that won't be found in the service manuals. This critical setting of the points on the Battery Capacitance Discharge models (1968/1972), that is "only" the models that incorporate points instead of sensors, is most important. Originally discovered sitting in a motor well on a very hot day in central Florida after a couple hours checking everything else on a tempermental mind destroying 1971 60hp Evinrude back in 1978. An experience one doesn't forget. Since that day, up to retirement, checking that critical setting first has saved me much time... and the customer much $$$.

 

[Jimbo's Jumbo]

I haven't had time to work on the motor due to work, but will hopefully have a chance in the next couple days.

Thanks Joe, I'll be sure to pull that flywheel and check them out and reset them if needed, and I do have a very good torque wrench (just need the attachment for that HUGE nut).
Anyone got a good way to pull it off without a puller, or a good place to purchase a puller that wont break the bank?

Still nothing about this Temp Switch. Anyone know anything about that? If that has nothing to do with the spark issue, I'd at least like to know what the heck it does (haven't had time to read the whole manual yet either).

Thanks again guys, you're knowledge is invaluable.

cobbcfi - sounds like you have an interesting job.

 

[Bosunsmate]

Im pretty sure the temp switch you a talking about is the hot horn alarm sensor.
If you are still dubious, then just check there are no wires to the back of the heads which arent connected to the coils or spark plugs or are grounds.
post a pix if you are unsure of something you find. Ive never come across a temp switch which kills spark, its always to a warning horn, apart from on much more recent motors

 

[cobbcfi]

You can rent a puller from Autozone, they will charge you full price for it in their "tool loaner" program and then refund you the money when you return it.. Just a suggestion