Here’s a head scratcher, my Mercury 80 is firing on multiple cylinders at the same time eg 1&3 , 1&4 ,4&3 etc changed switch box to another brand new one, same thing, change plug leads over so engine technically should not start but it does without banging and backfire etc !!! Borrowed genuine merc switchbox and no 1 fires on its own without no 4 simultaneously, no 2 fires on its own and so on, is there a known problem with the Chinese switch boxes ? Strobe light was also checked to make sure it was not faulty .
Any clues ? Marine technicians are puzzled on this one .

Is the new switchbox the same part number as the old? My 'suitcase' says there are 2 different part numbers depending on the coil colour...Could be barking up the wrong tree.

It comes to my attention that after my technicians had a “ chat” with Mercury on the phone, it comes to pass that the original switch box ( CDI unit) has a black compound material as opposed to the clear silicone of those built in China (therefore seeing all the components, coils etc), apparently, the silicone acts as a conductor hence making some of the cylinders fire simultaneously ?? as I mentioned on an earlier post, when an original unit was put on that I borrowed, all cylinders fired independently! So, whether it could be the different part no’s on the Chinese versions that Rapier mentioned ? who knows, but I was quite taken aback at that info given by senior technicians at HQ ! New genuine switch box now on order