switch box replacement

[twebb]

I replaced one switch box about 6 months ago, and I hear you should do both at the same time. Is it to late to do the other one now? motor has only run for about 5 hours since I replaced the first one. Or should I have the new one checked first? thank for the help

 

[Bondo]

Re: switch box replacement

Ayuh,.... What motor ya workin' on,..??

 

[twebb]

Re: switch box replacement

1986 mercury 90hp I6

 

[bilge rat jim]

Re: switch box replacement

Merc (and CDI) recommend that you change both switch boxes at the same time. They claim that a faulty bias circuit on the old switch box will affect the new switch box, causing failure. I have seen this only a few times, and always, the new switch box failed immediately upon start-up.
Disconnect the battery. Disconnect the White/Black jumper between the switch boxes and check the resistance from each boxes White/Black terminal and engine ground. You should read 14-15,000 ohms on both switch boxes. Any problem on the bias circuit and BOTH switch boxes must be replaced as a set. If both your switch boxes are within range, you will probably be OK.