My Mariner has 2 power packs(switchboxes) and had set for several years before I got it. When displayed on a spark card there was spark on all 6, but it was white, not blue. Long story short; trigger was faulty, Carbs had to be redone from residue the first thief left behind(disassembled and blew out with carb cleaner and charged $60 per carb)and one power pack was too weak to keep up with the other, and they need to be replaced in pairs. Fuel line broke down and fuel pump and filters had to be replaced.(and the line did it again a year later). It starts quickly now when cold and like an old chevy when warm. Sometime in the future, sooner better than later, have a GOOD tech run an electronics diagnostic on all your parts cuz it will never perform right til they are up to par. All the fuel system advice so far is spot on. My fuel lines let chunks of rubber into the system that blocked the JETS with no evidence in the bowls.