Still more 4 hp troubles (not fuel)

[GoldToyBox]

Need help ASAP the fish are biting!!!!!
4 hp 1988 Yamaha outboard. Starts ok, runs at idle for 10 minutes or 5 minutes at speed ... then just stumbles/fades/dies! Replaced plug, rebuilt carb (found nothing wrong with either?). Checked fuel flow from tank to carb ok. I will not restart unless I wait for 30+ minutes. Then the same thing? The vent is open (even removed the cap to be sure). Removed the tank, cleaned it, new fuel. Found nothing wrong with the tank or fuel. Now I believe the fuel is ok, When it died I shut off fuel valve and opened the bowl drain ... it was full of gas. Allowed the bowl to empty and opened fuel valve and fuel flowed from bowl again. So .......... I guess the problem is electrical? Engine runs until it gets hot and then dies.
Don't know what I should get for OHM readings on the coil, capacitor or mags. 90 miles to the nearest shop. Most likely culprut??
Any thoughts welcome.

[Ken]

GTB,
Well, you have done a lot of troubleshooting and have pretty well eliminated fuel problem. I agree with you now that it is most likely electrical. Something in the magneto circuit is heating up and expanding and then opening, breaking the circuit. The component in that magneto circuit that is most likely the culprit is the capacitor. Gonna be hard to test with an ohm meter. Check all connections in the magneto circuit that you can get to. Does the circuit have points? (I am not real familiar with magneto circuit on outboard - you really need a Yamaha shop manual if you can find one.) If it has points, check them and if they are pitted, try filing them down smooth.
Check the coil where the spark plug wire goes into it. If it is removable, check the contact surface of the wire and coil output. Sometimes this area can get corroded and cause problems.
Good luck,
Ken K

[GoldToyBox]

No points, electronic system.
I've pulled the top off to get to the componnets.
Found three coils:
one appears to be the "pickup coil" (magnets spin passed it. Reads 326 to 333 ohms
Smaller coil, reads 32 ohms
Larger coil, reads 290 ohms
No idea what the ohm reads should be?
No obivious problems seen visually.
All the wires from these coils feed into or from something called "CDI", a black box. Ohm reads from the CDI appear to show capicators in side but no positive.

Any help appriciated

[Ken]

GTB,
"CDI" stands for "capacitive discharge ignition". The coils you are looking at all together is called the stator. The magnets of the flywheel spin past the coils of the stator to generate necessary voltages for ignition and battery recharge (rectifier/regulator), though you may not have battery setup.
The most likely culprit would be the CDI unit -
it is expensive to replace and almost impossible to troubleshoot (mostly sealed). You need a Yamaha shop manual for the test procedure on the coils. If they check good and all connections to/from the CDI are secure, then you probably need to replace the CDI.
You say that you have to wait 30 minutes before the motor will start again - you might try spraying the CDI unit with a cooling agent (available at Radio Shack or electronics parts stores) right after it dies on you. If the motor cranks back up, then it's the CDI.
Good luck,
Ken K

[GoldToyBox]

Ken, Thanks for the help.
New CDI on order and a Yamaha Manual!