40hp ignition problems

[boatingnole]

I have 1986 40hp Yamaha that has intermitenten ignition problems. Sometimes it runs fine then other times it won't start and has no spark. I tried disconnecting the white wire from the cdi to key but doesn't seem to matter.
Can someone tell me how to check the cdi box?

[99yam40]

follow the steps in service manual using the proper test equipment.
the peak Voltage tests on the inputs and out puts of CDI while on the motor turning with starter are the best way in my opinion