No spark on 3rd and 4th plugs

[00reg00]

Hi i have a four cylinder mercury 50 hp 1979 serial number 09371951 can anyone help with any sugestions how to check the switch box or stater to see which if these are at fault as sparking on the top 2 cylinders and no spark on the bottom 2 cylinders, any advice will be grateful

 

[Laddies]

Re: No spark on 3rd and 4th plugs

It's propably te trigger or box if you don't have a DVA then OMH test the trigger first, here's a test for the complete system.