CDI unit failure

I have a 1985 40 hp yamaha that has blown 2 CDI units.This has always happened on first start up in spring.Motor ran fine all season-Winterized for storage(ran carbs dry,disconnect battery,battery tender)First start for spring-(fresh gas,hook up battery,turn key-no spark at any cylinder,tested coils-OK,CDI unit test bad)

I checked all wiring looking for shorts and all look good.The key is off when hooking up battery.What can be causing this problem.This is the second year in a row that this has happened,at $350 a shot I cant keep relacing CDI boxes every year.Please help -I can't figure this out! Thanks!

[boats.net]

Not sure, haven't had any problems with the CDI's. Check the Charge coil output to see is whithin specs.