2006 Yamaha 115hp 2 stroke Loss of power

[Bluebill]

My son bought a 06 Yamaha 115 2 stroke the motor is very clean and was always serviced. Last summer the motor ran fine with out an issue, service and put up for the winter. This summer runs fine until last week. Starts fine runs good top speed at 45 mph, then all of a sudden loss of power and it like bogges down, acts like no gas or no spark to two cyclinders. My son shuts it off fishes for 1/2 hour and starts up runs fine. He thinks it is a fluke. Does the same thing again just as he is backing off the boat lift running fine then start to rev up sounds like it is only half the engine will not get up pass 2500 rmp. We take it to repair shop, checks oil tank, fuel filter and he starts it all is fine. He thinks it is the CDI or some other electrical issue under the fly wheel. But does not want to order either part because he is not sure and they are expensive. So any ideas? Thank you in advance.

 

[ClassicAQ]

What I've found to be accurate and most useful when troubleshooting is a piece of advice given to me by a yamaha master mechanic....when the engine isn't giving top performance the start troubleshooting the fuel system because 90% of the time it's the fuel system where the issue resides, not spark or compression.

When was the last time the carbs were pulled and cleaned, including pulling jets?