Aren't my ignition coils defective?

[2strokes4ever]

Bought my yammies used. Never pushed their RPM too much. At first, at higher RPM they sometimes would surge for some time but never paid attention since they used to give me the speed I was happy with. Later one of them started sputtering and turning off, changed spark plugs, cleaned carburetors and that went away. Now bogging now happens on both twins every time I hit 3/4 of throttle no matter what. I even tried a clean can of ethanol free gas, new water separators, new fuel filters, and still bogging.

So I went and made sure all coil plugs were generating sparks with a spark tester on the port engine
My premix is fine
Also checked the resistance on the primary and secondary ignition coils and found about three had too low or too high resistance values as per the manual
I then fired her up and unplugged spark boots one by one and there were three where there was no noticeable change in engine RPM

Engines are Outboard is 225TXRR 1993 yamaha twins premix
Sparks are brand new and they all have that usual two oil slime
Have sprayed crab cleaner down carb throats when it is bogging and no change
Have pressed priming bulbs during bogging and no change either
And compression is good on all cylinders

Does anyone think that there isn't anything wrong with my coils with these results?

Doesn't this mean I most likely have some coils, or coil wires, or coil boots that are defective?

 

[99yam40]

I would get some Peak voltage readings for all the inputs and outputs of the CDIs to make sure they read at least the minimum listed in your service manual.
you mentioned that you made sure all pugs on Port motor had spark using a spark tester.
to me that means they were sparking.
what about the other motor?
proper fuel to air ration is very hard to test, too much or too little will not burn properly.

if they all have good compression, and good spark at the correct time.
then you are left with a fuel to air ratio problem at higher RPM.
I would inspect the carb bowls to see if there is water or debris causing a problem with the main jets

 

[2strokes4ever]

I would get some Peak voltage readings for all the inputs and outputs of the CDIs to make sure they read at least the minimum listed in your service manual.
you mentioned that you made sure all pugs on Port motor had spark using a spark tester.
to me that means they were sparking.
what about the other motor?
proper fuel to air ration is very hard to test, too much or too little will not burn properly.

if they all have good compression, and good spark at the correct time.
then you are left with a fuel to air ratio problem at higher RPM.
I would inspect the carb bowls to see if there is water or debris causing a problem with the main jets

The other engine boggs too but I haven't checked ignition coil resistances or cylinder drop test yet

So despite the out of range coil readings you lean more towards a dirty carb problem as the cause for the bogging at higher RPM? which I do think they need cleaning by the way

 

[99yam40]

I have no idea if your motor has low and high-speed charge coils sending voltages to the CDI, but taking those peak voltages should tell you if there is a problem if you do have separate low and high-speed charge coils.
with both motors doing it it is hard to believe both had the same type of coil failures at the same time.
test what you can

 

[Scott Danforth]

It's most likely NOT the coils.

 

[2strokes4ever]

So is it also right to say that it is most likely not a fuel line problem that I get failed cylinder drop test in those cylinders I mentioned?

 

[99yam40]

if there is not the proper fuel to air ratio in a cylinder even good spark cannot ignite it

 

[boscoe99]

There are ignition coil output testers.

There are procedures for misting gasoline into the intake system to troubleshoot for a fueling related problem.

There are those that troubleshoot by replacing suspect parts with new parts, hoping to stumble upon a solution.

 

[2strokes4ever]

Thanks for all the help

Is it then safe to say, that once I do fix the problem, I should not get a failed cylinder drop test in any cylinder?

So that even before I head out to the marina to test it under load, at home I'll be able to know by checking for cylinder drop test?

 

[99yam40]

checking at idle will not ensure there are no problems at higher RPM and under load

 

[stresspoint]

check the compression.
sounds like it may be a head gasket issue.

possibly an air leak around the intake manifold ,hit it with some either spray or carb cleaner around all the joins , see if rpm changes.

 

[boscoe99]

I have no idea if your motor has low and high-speed charge coils sending voltages to the CDI, but taking those peak voltages should tell you if there is a problem if you do have separate low and high-speed charge coils.
with both motors doing it it is hard to believe both had the same type of coil failures at the same time.
test what you can

It does.

 

[boscoe99]

Have the charge coils been tested for proper output to the CDI box?

Has the CDI box been tested for proper output to the ignition coils?

 

[2strokes4ever]

Correct me if I am wrong, but I think two strokes don't have intake manifolds. I'll check compressions again and report though

If when you say charge coil you mean the stator charge coil, I did check it a while ago. I'll recheck. Haven't checked CDI output to ignition coils because I believe a DVA adapter is needed for that and I don't have one. I also think those DVA readings must be taken under load? But I did confirm sparks in all cylinders with a coil spark tester.

 

[2strokes4ever]

Is there any significance to them bogging even more when I pushed them past 3/4 throttle last time I had them in the water? Does that help pinpoint the problem at all?

 

[Scott Danforth]

I would be looking at the carbs and fuel system

 

[boscoe99]

Correct me if I am wrong, but I think two strokes don't have intake manifolds. I'll check compressions again and report though

If when you say charge coil you mean the stator charge coil, I did check it a while ago. I'll recheck. Haven't checked CDI output to ignition coils because I believe a DVA adapter is needed for that and I don't have one. I also think those DVA readings must be taken under load? But I did confirm sparks in all cylinders with a coil spark tester.

host pictures

 

[2strokes4ever]

host pictures

Oh yeah, right behind the carbs. I'll spray them and see if RPM picks up. I've sprayed the carb throats to see if I can find signs of fuel deprivation and found no changes, does that count? And if there is an air leak there at the manifold it would be because the carb bolts are loose?

 

[2strokes4ever]

I would be looking at the carbs and fuel system

Will

 

[99yam40]

get the DVA or other meter to get the peak voltage reading to make sure everything is doing what it should on the electrical.
test what you can and if no problems found with that then chase the fuel