85esl74b

[mvabate]

Need a little help. I ran a compression test on my 1974 85hp Johnson. They were 100psi. But I did it without grounding my plug wires, and now I'm not getting any spark. Where should I start. Thanks

 

[mfkadz]

Cranking with the plugs out and wires disconnected should not effect the system.

Are plug wires seated correctly?

Did you bump, remove or otherwise change anything in the process?

How are you determining there is no spark?

mike

 

[mvabate]

A little back story. I rebuilt my carbs last year because it was having a hard time starting. Winterized it(sits outside in the Midwest) and fired up really well first time of this season. If I don't pull the fuel line after running it, it gives me problems. So now it'll crank and crank, wouldn't kick over. Fuel was getting to the carbs, but leaking out the front. I did a compression test, cause when I pulled the old plugs, one was dry. I also pulled the carbs, drained the gas, and check operation of float.(blowing in line when flipped over). Checked out ok. Checked spark with spark plug grounded out. Nothing at all four. I did find one bad coil, and another coil with higher resistance than specs allow. I appreciate the help. I am slowly learning about this outboard

 

[mvabate]

I did use a neighbors homemade spark tester, maybe the plug wasn't compatable with my electrical system. I just picked up an adjustable gap spark plug tester. I'll see if that was my issue with the spark

 

[mfkadz]

You should use the recommended plug in these motors. Champion QL77JC4.

I got mine at O'Reilly.

 

[mvabate]

Thanks, I use the correct ones for the boat. I was saying the homemade spark plug tester had a plug we plugged in to the boot. I'm sure that wasn't the correct one

 

[emdsapmgr]

That engine has to crank at least 250 rpm's in order to fire the spark plugs. The coils are pretty reliable, also, it's unlikely that all 4 failed at once. So it's another ignition problem. The other components in the ignition system are timer base, the stator and the power pack. You'd want to qualify the stator and the timer base first, and then by a process of elimination-finally repl the pack. If you are handy electronically, you can do your own testing. Check out this website: cdielectronics.com.
They have some excellent troubleshooting info for your engine. Pay attention to testing the timer base and stator by the cranking test-which will create voltage outputs. You'll need a special "peak reading" voltmeter to read valid voltage info-a normal household meter won't work.

 

[RandyJ]

If you've got a digital volt meter (multimeter) and an analog meter it's fairly easy to check out the system. You'll get an A/C current from the stator to the rectifier then a DC current from the rectifier to the power pack. The power pack puts out a pulsing charge to the coils which you can see on an analog meter. Once you find a part that is putting out an electrical current you've found the culprit. There are variations on this scenario but that's it in a nutshell.

 

[mfkadz]

Thanks Randy, I wish I had thought about the analog meter when I was shooting my issue the last few weeks. I was not up for getting the uplevel DMM. I have a nice roll top that was my dads. from the 50's? 60's?

mike

 

[mvabate]

Thanks for the input. The CDI website is fantastic. The idea for an analog meter is a good one. Did you guys purchase a peak voltage reader, I found a link on how to make an inexpensive one. Any thoughts

 

[emdsapmgr]

I purchased the special DVA meter. No need to, I've also got a small plug in adapter converter-a cheaper option.

 

[mvabate]

Thanks I do like the cheaper options. Randy J can you explain a little more about your current theory. But no so much in a theory kind of way. Are you saying those components should not produce a current, and when they do that indicates a bad one?

 

[RandyJ]

My experience (shade tree style) is that the stator is much like an alternator on a car. Its output is AC current. Generally (at least on old merc's) two yellow wires come from the stator to a rectifier which converts the AC to DC. The wire coming out of the rectifier supplies the charge to operate the electronics of the engine. If there is no output (12 volts or greater) the rectifier would be bad. This is also where the charge comes from that keeps the battery charged and powers the CDI unit a.k.a. SCR. On Johnnyrudes they're called power packs, on mercury's they're called switch boxes. The electronics in that box tells the coils when to fire so you'll get a pulsating DC output to the coil(s) causing the needed to jump on an analog meter set to read DC current every time a voltage output is sent to the coil to spark a plug. If there is no output to the coil(s) you have a bad SCR. A cheap analog volt meter can be had for around $10 and solve a few mysteries. Of course, if you have DC pulsing current to the coil(s) and no spark then you have a bad coil. Off the top of my head I can't explain how a trigger mechanism works but I do know the CDI website does cover that pretty well. What I have given you is pretty much the same for a lot of older outboards like I have experience with ... 25-40 years old and older. A DVA isn't really necessary but definitely is handy and for some diagnostics is essential. I have one and went to the CDI school a couple of years ago. So far I have used a DVA exactly ONE time and it told me what I needed to know. In that instance the rectifier was bad in an old merc. Cranking an engine without grounding the plug wires puts a load on the coils and can blow a coil or SCR. On a Johnnyrude I'd bet its the SCR in the powerpack but do not run out and buy one without first verifying that there is a charge to the powerpack and no charge coming out. With your cheap analog meter black lead to ground on the engine and red lead to the wire which runs to the coil... check each coil the same way. Caveat... I don't know if this scenario applies to your engine or not as I am not familiar with the configuration of your particular engine and would have to research it to confirm if this information is applicable... the theory is much the same and is adaptable to most engines that are not equipped with a distributor and are controlled by a CDI (SCR) unit.

 

[racerone]

Sorry , I do not believe that current goes from the rectifier to the powerpack.-----------Rectifier is on the battery charging side.

 

[mvabate]

Thanks for all the input! As soon as I get some free time(not working on my wife's work or pleasure vehicle) I'll give it a go. Just picked up a cheap analog meter, see if it'll help me pinpoint my issues. I'll post what I find