1982 50 HP Mercury ignition switch box.

[Dean36]

Hi ya all
I bought a new switch box for this motor. A warning note came with the switch box stating that I should find out what cause the switch box to go bad before I install the new one. It also said "such as an over charged battery". Looking at the manual, I can't see where a type V ignition uses the battery. All the key switch does is disconnect the ground on one of the box's terminals.

TWO QUESTIONS:

1. How can I find out what caused the box to fail ?

2. Am I missing something on the battery connecting to the ignition?

Thank much for your time.

 

[eaglelakewally]

Re: 1982 50 HP Mercury ignition switch box.

hey dean36, you should look into what may have caused the fault, just changed my bad switch and would have thought nothing until I saw that warning note included. Long story short my rectifier was bad, probably would have burnt a new box if it was not discovered..

 

[sschefer]

Re: 1982 50 HP Mercury ignition switch box.

This is a great question and one that's often overlooked. What I understand and read in the shop manuals is that the rectifier actually acts as a protector. If the battery terminals are accidently reversed the rectifier blows saving the switchbox. The theory is that it's the cheaper of the two parts. People will argue that the rectifier is not part of the starting circuit and should not effect the switchbox and that is correct to some extent. But, if you hook up the cables backwards and put 12v + to ground the rules change.

Three other things that can damage a switchbox are a bad coil, bad stator and excessive heat. The stator would need to be spiking indicating a short. Shorted stators most commonly occur after an severe overheat when the insulating coating on the stator coil windings melts and the windings short to each other. You might see this as lower than spec stator resistance readings or as high DVA readings.

So if you remember a time when you accidently crossed your battery cables, check your recitifer or the problem may still exist after your change the switchbox. Then check you're coils and stator for proper resistance and the output voltage of the stator.

Lot's of folks seem to get lucky and the swtch box change does the trick. Luck never seems to follow me so I just bite the bullet and do the checks.

 

[Dean36]

Re: 1982 50 HP Mercury ignition switch box.

Thanks guys for the good info it was a big help,
I started restoring this boat last year and I have completely re-wired the boat. It came with a bad rectifier which I replaced. The motor still ran rough. I re-built the carburetors------ still ran rough. I had checked the compression before I bought the boat and it was good on all four cylinders. Then the motor got to where it wouldn't even start and I found that I had no spark. I checked the resistance of the stator and the trigger coils. They were all within specs and no continuity to ground, which is why I laid out the $183 bucks for the switch box. The motor now purrs like a kitten. My questions now are:
1. Could the bad rectifier cause the switch box to start going bad? Are did the switch box go bad after I had changed the rectifier? Do I still have a problem?

2. Is the rectifier just two diodes with connected cathodes are is there some kind of a voltage regulator inside the module? What is the best way to check it?

3. What maximum voltage should the stator put out when connected to the battery?