Mercury 40hp 1980 Switch Box is Bad

jayard78

Petty Officer 2nd Class
Joined
Dec 28, 2008
Messages
101
I have been troubleshooting a motor I bought (Mercury 40hp 1980 2cyl 2stroke) and have found that there is only spark coming from one power pack. I troubleshot the power packs that the plug wires plug into and they are ok and since I am getting spark out of one wire I am ruling out the magneto.

All leads back to the switch box which has been a concern since the beginning do to the HIGHLY corroded wires coming out of it. Today me and a friend decided to try to rebuild it by cutting out the rubber filling the switch box to get to the circuitry and found that one wire had completely desintegrated. It had turned into rusty dirt and dust. Another wire was almost as bad but after digging it out a couple inches we found a good section to soder into. Our attempt failed though and we still only had spark coming from one power pack (the one that has the green wire w/ white stripe coming from the switch box). When plugging in the all green wire to any power pack (coming from the switch box) we get nothing.

So I have been quoted by a local salvage guy $195 for a new switch box. Shall I bite the bullet here?
Does the spark diagnosis seem correct?
Anyone an expert on these switch boxes?

Thanks.
 

Laddies

Banned
Joined
Sep 10, 2004
Messages
12,218
Re: Mercury 40hp 1980 Switch Box is Bad

The boxes are none repairable in the field. Ohm test the trigger and stator first but it does sound like the box and it's shot now anyway.
 

jayard78

Petty Officer 2nd Class
Joined
Dec 28, 2008
Messages
101
Re: Mercury 40hp 1980 Switch Box is Bad

Sounds like a plan, thanks then. I'll post back after installing it to see let you know if it fixes the spark. BTW do these switch boxes come with a wiring diagram or do I have to fine one online some where.:cool:
 

jayard78

Petty Officer 2nd Class
Joined
Dec 28, 2008
Messages
101
Re: Mercury 40hp 1980 Switch Box is Bad

The Switch box fixed my spark issue. New problems have arrived tho. I will start a new post.
 
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