Diagnosing no spark issue on 1992 mercury 8 hp. 2 cycle

[billy-j]

Hello. Would anybody here have Mercury technical knowledge regarding a no spark condition on a 1992 merc 8hp. 2 cycle model # oG20073 . Specifically Mercury step by step knowledge on how to check each component of the electronic ignition. There is no spark on either of the 2 cylinders. I do not have a Mercury specific shop manual and a Clymer manual just does not make it. Thank You Bill,

[crosbyman]

did you check utubes   maybe somebody fixed one … when did this start happening.

you  have a electronic ignition  so anything goes…  switch box  trigger

dual plugs..coils wires likely did not fail  together so you are back under t e flywheel.  kill switch could cause a problem

see page 76 -77    in this doc. .. all this requires  testing  skills with thenecessary eqpt. (VOM)

CDI Troubleshooting Guide – 2012.pdf (cdielectronics.com)

 

this is kind of a modern engine  🙂     Hopefully  experts will chime in … try alsos the IBOATS site for help .

 

 

see video on a Mariner problem to show what is involved here   the CDI  switch box is frequently the culprit has tested in this video

8 hp Mariner – Diagnosing a bad CDI with an Ohm Meter “No Spark ⚡️” – Part 1 of 2 (youtube.com)

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1 user thanked author for this post.

billy-j

[billy-j]

Yes, I know it’s kind of a modern engine. Only 32 years old. (It makes me feel old cause I think it’s brand new). I live in the Cleveland Ohio area and there are not many marina stores left around here for support for engines of this era. Plus, parts are very expensive to just replace parts you think are bad. I just thought it was worth a try here that someone was familiar with this era of motor. Regards Bill,

[crosbyman]

check in on IBOATS  folks  .. user RACERONE  is probably the top tech   and may answer your  questions or try the search utility

Mercury & Mariner Outboards | Boating Forum – iboats Boating Forums

 

anything special happened before the failure ?   Did you try  a kill button running at high rpms  ?

what are your  “electrical” testing skills ?

Dave Bernard here  on AOMCI may pop in.  he his the Merc   man !

 

another site to look for help is    Johns’s old mercury site . no certain if membership is mandatory for  questions but that is where Merc  folks hang out 🙂

JohnsOldMercurySite – Index page

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[crosbyman]

this may solve the problem

Amazon.com: Outboard CDI/Ignition Pack For Mercury 1980-1997 6 8 9.9 10 15 20 25 35HP 114-7452K1 18-5777 18-5778 9-25102 339-7452A1 A7 A8 A9 A10 A11 A14 A15 A18 A19 A20 A21 Engine Using the Bullet Connection Pack : Automotive

 

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[billy-j]

Hello Crosbyman.  Already talked to Dave Bernard. He said too new for him. I have talked to him before he is a nice guy.  Motor was running good and very reliable. Shut it off normal and the next time would not start. It has a couple of kill switches on it and I was told there might be one more. Too much safety for my likes. But it has been a reliable motor for years. I am sure the problem will reveal itself eventually. Thanks again. Bill,

[crosbyman]

ok good luck with the motor   keep us all in the loop on the aches of your  “new” motor. 🙂

 

just fyi   the phase maker ignition (Thunderblot) using points  would fire on points CLOSING contrary to  magneto convention.

the  CDI  circuit was known to blow when the kill button  was used when RPMS  where high.   With  more modern  CDI like yours  with  no mecanical points  (uses a trigger pulse coil) I am not educated enough to know if  the CDi could … be kill if  interrupted at higher rpms.

If you are able to measure specs on the trigger  and  the  stator as per  the Video and the CDI book  I strongly suspect the CDI box itself.

thankfully they don’t seem to expensive on Amazon compared to OEM at 300$

 

fyi  bed time reading 🙂

https://wrcoutboards.org/wp-content/uploads/2021/02/The-Phase-Maker-CDI.pdf

Microsoft Word – Generator Coils Explained.doc (wrcoutboards.org)

 

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[Michael]

Disconnect the kill wire from the switch box, it should have a black wire with I think a yellow tracer.

Doubt it is the coils.

If still no joy then it is something under the flywheel or the switchbox.

 

[seakaye12]

Hi,

I’m not a Mercury trained tech but I was working on a 1981 25HP Mercury the other day and it appears to have an ignition system essentially the same as your 8HP.

Since you have no spark on either cylinder….I would feel that you can rule out the coils.  It would be unlikely that both of them have failed.

I have attached some data.  Also the CDI troubleshooting PDF for the Stator.

Most of the tests require only a VOM;  the stator voltage tests are harder to do unless you have a test tank and can run the engine at WOT with a DVM attached.

As Michael stated above…..the very first thing you want to do is disconnect the kill switch at the switchbox.  That could very well be the problem.

 

[Matthew Pieklik]

CDI Electronics has a trouble shooting guide that might help you out. I’m sure they make the parts you need to get your future vintage outboard running.      www.cdielectronics.com     Google it and you will see the trouble shooting  listing to click on.

[Author]

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