MERCURY 70 BLOWING SWITH BOXES

[boatmike]

I HAVE A 1979 MERCURY 70 WITH THE THUNDERBOLDT IGNITION. ABOUT 30 DAYS AGO THERE WAS NO SPARK GOING TO ANY CYLINDERS. I TRACKED THE PROBLEM TO THE SWITCHBOX AND REPLACED IT. FIRED UP ON FIRST START. NOW, ON ONLY MY THIRD TRIP OUT, IT WOULD NOT START AGAIN. TOOK IT HOME AND FOUND SAME PROBLEM AS BEFORE. CAN ANYONE TELL ME WHY MY SWITCHBOX KEEPS GOING OUT? CAN'T AFFORD TO KEEP BUYING THOSE THINGS! <br /> THANKS, MIKE

 

[Trent]

Re: MERCURY 70 BLOWING SWITH BOXES

Couple of things come to mind. Bad grounds are one cause. Second is the charging system going above 17 Volts?? Overcharging can blow the pack (switchbox).

 

[boatmike]

Re: MERCURY 70 BLOWING SWITH BOXES

THANKS FOR THE TIPS. IF THE CHARGING SYSTEM IS OEVECHARGING, IS THERE A TEST I CAN DO WITHOUT THE MOTOR BEING ABLE TO RUN, OR DOES A NEW VOLTAGE REG. FIX THAT?<br /><br /> THANKS, MIKE

 

[ebbtide176]

Re: MERCURY 70 BLOWING SWITH BOXES

^

 

[Trent]

Re: MERCURY 70 BLOWING SWITH BOXES

Couple of other things to think of. When an engine starts blowing power packs repeatedly, especially on the same cylinders, replace the ignition coils on those cylinders. The inductive kickback from a bad coil can destroy the packs, even if the coils check good with all known tests. A stator that test good can also be sending spike voltages to the packs causing them to fail repeatedly.