50 hp 4 cyl rectifier questions

I'm working on an older 50 hp 4 cyl 2 stroke (6307771) .It lost fire on two cylinders. after checking dva voltages, I determined switchbox to be bad. Replaced and it ran fine for two outings then lost fire on 2 cylinders again. again dva readings pointed to switchbox. I pulled flywheel to check wiring from stator. The 2 yellow wires from stator were corroded and insulation coming off. Changed stator and switchbox. It seems to be running fine now but would like to check rectifier to avoid anymore problems. How do you verify proper function and could a faulty rectifier cause these problems?

Check it using this methodor put a volt meter on the battery terminals and see if (running in water) the voltage goes up at 1/2 throttle and above.

Thanks