1989 Mercury 25 hp Power Pack CDI question

[w2much]

New to me engine had no spark. PO told me the power pack was bad. He had replaced the trigger with a new one but the pack was not producing spark. I had a good used pack to replace the bad one . Installed the replacement . Pulled on the starter and had spark in both cylinders. I was a happy camper was a few minutes. I only pulled a few times when one cylinder lost spark. I am hoping I did not ruin the pack . I switched coils and determined that the pack is not producing spark for one cylinder. I am curious if a bad stator or trigger or something would ruin a pack after just a few pulls to the starter.

 

[25xs]

Having replaced at least 15 Mercury 2-cylinder stators on those engines, the symptom you describe is common when a stator is bad. It has a high speed and a low speed signal to the "switchbox" (OMC engines have Power Packs...) and you likely have a shorted out, low speed signal from the stator.

http://www.iboats.com/Mercury-Marin...9978061--session_id.640419545--view_id.335879

It's an easy replacement, BUT you will need to buy a flywheel puller from an autoparts store, then you will need three metric bolts and some large washers that are not the ones included with all the flywheel pullers I have purchased. DO NOT screw the puller bolts into the flywheel deeper than the hole, or you can run them right into critical parts under the flywheel because the holes go clear thru.
Clean the threads of the stator mounting screws on a wire wheel and ad thread locking compound (Red LockTite) upon installation. You'll never be under the flywheel again, so permanent LockTite is fine.
Tom

 

[flyingscott]

I have never had to replace a stator on those motors. They really only have a pick up and driver coil under the flywheel and are very durable units. The fact you have spark leads to the fact that you have a signal from the stator. I would check all the wires make sure they are not rubbing or bare anywhere. Check all your grounds and check the spark plug ends for corrosion. It is also possible your replacement switchbox went bad. On most of those motors when you lose one cylinder 9 times out of 10 it's the switchbox pretty common for that age. Don't use red loctite to bolt the stator down because if you do need to pull the pick up or coil off the bolts are small enough that you can snap them off. Blue loc-tite works fine. www.cdielectronics.com has the instructions for testing your ignititon components.

 

[25xs]

I have never had to replace a stator on those motors. They really only have a pick up and driver coil under the flywheel and are very durable units. The fact you have spark leads to the fact that you have a signal from the stator..

The single cylinder sparking might be weak attempt by the high speed windings to energize the SCR inside the switchbox at low rpm... Again, I own three DVA meters, I use them religiously to diagnose this particular ignition following the CDI Electronics guide mentioned in the posting above on nearly a monthly basis over the past 15 years in recreational as well as racing service. Several of the two cylinder switchboxes in my inventory are perfectly good "take offs" from unsuccessful repairs by owners and other shops after I replaced the stator. I also feel that the readings listed in the CDI Guide are a little bit conservative and seem to get readings a little higher than the upper end of the range listed.

That said, I agree anyway with FlyingScott about using the proper tool (DVA Meter) and taking the time to familiarize yourself with the (pretty simple) ignition system and diagnose it methodically. You may even "enjoy the hunt" for the bad component causing your issue. The problem is that you'll need a "Peak Reading Volt Meter" (DVA Meter) and it's really not found in any mechanics' toolbox with the exception of a competent marine mechanic... You can buy the DVA Adapter tool from this site: http://www.iboats.com/CDI-Peak-Read...84758771--session_id.954000650--view_id.38060

 

[w2much]

I need to learn to use the DVA that is certain. I purchased a DVA adapter but have not familiarized myself with its use. I am electronically challenged. I do use some of the functions on my analog multimeter but have not figured out my digital multimeter. Could I have ruined the switchbox in just a few pulls of the starter ?

 

[flyingscott]

You will have to do the tests to find out if that occurred. You don't need the DVA for every test you can do the resistance tests with out it and your analog meter should work fine for those.

 

[w2much]

I guess I am moving forward. The digital meter had a blown fuse. The stator and trigger can be tested wo removing them? They are resistance test?

 

[flyingscott]

http://www.cdielectronics.com/support/ Everything you need to know will be here some are resistance tests some aren't. They have very detailed instructions and are downloadable so you can print them.

 

[w2much]

Thank you. DVA readings are at cranking speed or idle of it runs?