Boggs down and wants to stall at around 1900 rpm

[toddingalls]

Thanks for the reply.
Have not been able to check timing while problem is occuring.
The alarm sounds when I pull the float in the oil reservoir.
Spark plug tester shows no spark on 1 and 3, but the plugs test good.

The timing light shows timimg bouncing around on different cylinders (friend/mechanic did this part, I did the rest of the testing)

[99yam40]

Not sure about that motor, but it may have a high and a low speed charge coil. Does your manual specs show it that way?
If so the high speed charge coil could be the problem.

Do you mean 1 & 3 has no spark any time or just some times?

There are ohm tests/specs that may show a problem, but voltage testing is best in my opinion. The proper test equipment and test harness would make it easy, but you can back prob the connectors with small thin pin/prob without hurting the insulation to get the readings

[toddingalls]

My manual only shows only 1 set of coils.
Coils test okay when I swap them to the other side.
I have no spark on 1 and 3 at all (according to spark tester)
Where can I find instructions on how to test the cdi with my ohm meter?
I am ordering the DVA adapter for my multi-meter today. But, I don't really know how to use that either.

[99yam40]

The charge coils I was speaking of are under the flywheel along with the pulser coils and lighting coils. These are the inputs to the CDI and battery charging. should be able to get to the wires where they go to CDI

There should be specs in the manual that give the ohms and minimum peak voltages, also should give colors of wires to check between.But I have not looked in an after market manual to see what they print. May need to pick up a Yamaha service manual if your does not give the info.

Here is something to read on testing and it may give you enough info, but a manual is good to have as it gives steps and pics.
CDI Electronics Practical Outboard Ignition Troubleshooting - page 124

[toddingalls]

Thanks!
I ordered a yamaha manual and a DVA adapter so I can test the different components.
fyi for others, that link just goes to pg 124
Here's the link to the full book (Yamaha starts on pg 97)
CDI Electronics Practical Outboard Ignition Troubleshooting

[toddingalls]

Okay... Follow up post (which MANY threads on this forum are lacking)
Replaced the CDI and motor is running great now!

[99yam40]

Good to hear you are up and running again.
Apparently you had good inputs but bad output voltages

[yamaha-115-96]

Late reply

I have issues with same engine, 115hp, 1996. What I want to know and maybe others, is IF the costly CDI-box is the culprit.

A DVA (peak voltage meter) is needed for good voltage reading on the CDI-box. You can easily build such a device:

1. a 1A, 400V rectifier diode connects - on the (white line) output side, to the positive (+) side of a 22uf, 400V capacitor AND 1 Mohm, 0,25W resistor
2. the negative side of the capacitor AND the other end of the resistor, are connected to a "negative (-) wire"
3. the positive output from CDI is connected to the (+) input (NON white line) side of diode. The negative output from CDI is connected to "negative wire".
4. The "peak reading" is made with a multimeter, DC range 200V, connected with red probe (+) , to the OUTPUT side of diode. The black probe (-) , to the "negative wire".
5. This DIY-instrument can also be used to take "peak voltage" AC from stator-, trigger-/pulser- and battery-charging-coils.
6. BE CAREFUL to build the device robustly into a safe box, and NEVER TOUCH the leads, as the capacitor can discharge quite unpleasant currents

The output CDI "peak" voltage on the 2-stroke, 115hp Yamaha, shall be 95 or 125 V , at cranking > ~250 rpm, depending on model. It is measured between B/W wires leading to ignition coils AND ground (B). Make sure the CDI-box is grounded.

Material cost for "peak voltage reader" = ~3$

[toddingalls]

Thanks for the reply! Might have to try this homemade DVA.
The DVA adapter that I purchased on ebay won't give me an accurate reading anymore... the voltage just keeps bouncing around on the meter.
Does you or anyone else know if the connections need to be soldered on the homemade DVA? Or is it possible to just use some type of wire nut?

[99yam40]

it will work either way, but soldering will make sure you have a good connection and will not loose continuity due to corrosion like wire nuts.

[yamaha-115-96]

block terminal

Hi !

I just used these simple plastic block terminals and connected the components and put it into a small plastic box, used for bicycle repair items. Just not to come in touch with the components, that otherwise, according to some could give you a nasty chock (mainly the capacitor) , if you accidentally hold them when the capacitor hasn't discharged.