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Switchbox Merc 115

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Dave Ervin

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"I have a bad switchbox. There

"I have a bad switchbox. There are 2 on my 81 merc inline 115hp. My question is, do I need to replace both of them? I have been getting mixed answers. Some say replace both, some say only the bad one. These are mercury parts, not after market.
Thanks,
Dave"
 
"Dave, there is no hard and fa

"Dave, there is no hard and fast rule, however, from experience most guys will tell you to replace both.

They are fed in common and if one went bad the other could have also been damaged to some extent. The switchbox is basically just a rectifier and capacitor and doesn't like wild/too much voltage coming into it. Kinda like headlights on your vehicle - always seems that when one goes, the other quickly follows.

So while the one that is still good may last a "little while" longer, it could well go on you in the very near future and take out the new one you just installed as well.

So just kinda think of it as insurance, since you will probably have to buy two packs in the end anyhow.

I would keep the one good one on-board though as a spare to get you out of a jam on the water..."
 
"Only both. And the stator, to

"Only both. And the stator, too. (A17) I never replaced one peice. You will end up wrecking the new part a lot of times. Wild voltage from the stator hi-speed windings is very common. The boxes need to be a matched set to work right, and without damaging each other."
 
"Thanks Graham and Bandit,
I

"Thanks Graham and Bandit,
I will replace both.
Dave"
 
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