16 Volts - Too High??? Mercury 60hp OB

I've got a 1986 2-stroke Mercury outboard 60hp. The engine runs great but the voltage is too high. The last trip of the season last year my GPS charplotter kept shutting off due to over voltage when run at 2000+ rpm. The engine was putting out over 17V!!!!

The first thing I did this year was install a new rectifier. I fired the boat up in my back yard and it is still putting out what I think is too high a voltage. It is outputting 15.5-16V at a high idle. I havn't put it in the water yet so I'm not sure what will happen then.

Is the voltage too high? Can someone steer me in the proper direction if it is??? Thanks!

Re: 16 Volts - Too High??? Mercury 60hp OB

Mercury60 said:

I've got a 1986 2-stroke Mercury outboard 60hp. The engine runs great but the voltage is too high. The last trip of the season last year my GPS charplotter kept shutting off due to over voltage when run at 2000+ rpm. The engine was putting out over 17V!!!!

The first thing I did this year was install a new rectifier. I fired the boat up in my back yard and it is still putting out what I think is too high a voltage. It is outputting 15.5-16V at a high idle. I havn't put it in the water yet so I'm not sure what will happen then.

Is the voltage too high?

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Absolutely it's too high. Installing a new rectifier will not solve it since a rectifier only converts AC to DC. It does not regulate.

We suggest installing a combination regulator/rectifier. Part# is 194-5279 List price is $158.00. We sell direct or you can purchase through iboats.

In addition, we highly suggest installing a new starting/cranking or dual purpose non-maintenance-free battery from a marine outlet. Avoid the supermarket & automotive store brands.

Why a combination regulator/rectifier & a new battery including the suggested style of battery? Read:

Battery Charging Issues, Regulator-Rectifiers and Tachometers

Re: 16 Volts - Too High??? Mercury 60hp OB

Thanks for your input but a quick question. How am I supposed to mount this?

My current one looks like this:


The one you are suggesting I install looks like this:


Also, do the wire just swap over color for color?

Re: 16 Volts - Too High??? Mercury 60hp OB

If you can, find a spot above the carbs to mount it. Ideally, the mounting space must have a good ground since the regulator's case gets its ground through the case. Also make sure the regulator is mounted securely.

Yes, the wires swap color for color. If the additional red wire is not needed, tape it off. If there is a gray wire attached to one of the rectifier's Yellow wires, attach it to the regulator's gray wire. If you do not have a tachometer, tape off the gray wire.

Re: 16 Volts - Too High??? Mercury 60hp OB

CDI Tech Support said:

If you can, find a spot above the carbs to mount it. Ideally, the mounting space must have a good ground since the regulator's case gets its ground through the case. Also make sure the regulator is mounted securely.

Yes, the wires swap color for color. If the additional red wire is not needed, tape it off. If there is a gray wire attached to one of the rectifier's Yellow wires, attach it to the regulator's gray wire. If you do not have a tachometer, tape off the gray wire.

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Wouldn't it be better on the battery and electronics if the voltage sensing circuit was connected to the postive battery lead like it's supposed to be? It's extremely simple to do.

Re: 16 Volts - Too High??? Mercury 60hp OB

sschefer said:

Wouldn't it be better on the battery and electronics if the voltage sensing circuit was connected to the postive battery lead like it's supposed to be? It's extremely simple to do.

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The extra red wire is not a sensing wire. It's an accessory wire...normally only needed to connect to a rev limiter (or another component that requires 12VDC).

Re: 16 Volts - Too High??? Mercury 60hp OB

This looks like a great product, and I'll seriously consider it, but what would cause my voltage to run high in the first place? For years Mercury didn't use regulators in these engines and they got by just fine.....I'm assuming they all didn't have 16V while running. I'd rather not just treat the symtom but I'd also like to treat the cause.

Re: 16 Volts - Too High??? Mercury 60hp OB

Mercury60 said:

This looks like a great product, and I'll seriously consider it, but what would cause my voltage to run high in the first place? For years Mercury didn't use regulators in these engines and they got by just fine.....I'm assuming they all didn't have 16V while running. I'd rather not just treat the symtom but I'd also like to treat the cause.

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Great questions. Unfortunately, many manufacturers in those days gave no consideration for what would ultimately happen to the customer's battery, rectifier & stator.

Per our Battery Charging Issues, Regulator-Rectifiers and Tachometers guide:

In non-regulated applications (rectifier only), the battery acts as its own regulator. When it can no longer regulate proper voltage from the rectifier, usually due to dead and/or weak cells, it needs replacing.

In this case, it is recommended to replace the rectifier with a combination regulator/rectifier and replace the battery with a dual purpose or cranking/starting non-maintenance-free battery. This way, the battery will no longer have to regulate. The regulator/rectifier will take that responsibility, thus giving the battery an extended life.


In those days, the batteries that were more readily available were the non-maintenance-free types (the lead acid types), which are ideal for outboards. But even over time, those type batteries will eventually no longer be able to regulate itself in a non-regulated application.

Nowadays, the maintenance-free batteries are the more readily available type (because they are sealed & are environmentally-friendly), so we are seeing MANY more charging issues because of these type of batteries that are used.

Regardless of which type of battery is used, a non-regulated application will eventually cause any battery to no longer be able to self-regulate. Batteries have no circuitry to regulate nor is designed to regulate.

That's where the combination regulator/rectifier comes in. It along with the suggested type battery (trickle-charged off a battery charger overnight before each & every use of the boat) will give your entire charging system optimum life.

Re: 16 Volts - Too High??? Mercury 60hp OB

CDI Tech Support said:

The extra red wire is not a sensing wire. It's an accessory wire...normally only needed to connect to a rev limiter (or another component that requires 12VDC).

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Interesting.

Re: 16 Volts - Too High??? Mercury 60hp OB

So is the 16V I am seeing considered normal for a mid 80's engine? If not, it is a sign that a my stator is going bad?

Re: 16 Volts - Too High??? Mercury 60hp OB

The stator cannot fail by putting out more voltage/amperage than its maximum rating. What the CDI Dude is saying is true; once the battery charges up to its 'normal' operating voltage, the charging system is still working 'overtime'. The faster you run the motor, the more power is generated. This is a very simple, trouble-resistant system and that's why Merc used it for years and years.

However, more "modern" motors, sensitive electronic accessories, and batteries do much better with a regulated system and that's what he's suggesting, is to retrofit the combination rectifier/regulator assy.

Your stator is rated to output around 10 amps max and the regulator will hold voltage in check to limit charging amps to a reasonable level.

Other than installing a regulator/rectifier, the only way to help with the issue is to load down the system. Try turning on your running lites and see if that makes any difference in output voltage. You're not gonna hurt anything by trying, and it might be enough.

HTH............ed

Re: 16 Volts - Too High??? Mercury 60hp OB

Thanks guys! I really understand what the heck is going on now. Its good to know that I'm not up sh*ts creek due to the 16 volts. Its also good to know that the stator is acting normally.

The only electrical devices on this boat are a gps chartplotter/fishfinder and the running lights. Sooner or later there will be a stereo but thats down the road.

For now I'll just start putting some cash aside for the rectifier/regulator to keep the chartplotter/fishfinder happy. Thanks again!

Re: 16 Volts - Too High??? Mercury 60hp OB

Mercury60 said:

So is the 16V I am seeing considered normal for a mid 80's engine?

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16V isn't normal for ANY 12V DC operation. 14.4V DC is the accepted prolonged max voltage for most 12V DC operations.

Mercury60 said:

If not, it is a sign that a my stator is going bad?

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A stator's battery charge windings are only put in jeopardy when a regulator and/or rectifier remains shorted internally. And what normally caused a regulator and/or rectifier to short is when a battery is overcharging over a prolonged period of time.

Re: 16 Volts - Too High??? Mercury 60hp OB

emckelvy said:

Other than installing a regulator/rectifier, the only way to help with the issue is to load down the system. Try turning on your running lites and see if that makes any difference in output voltage. You're not gonna hurt anything by trying, and it might be enough.

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And that's a band-aid. The only way to fix an overcharging issue is install a regulator/rectifier AND install a new proper type battery.

Re: 16 Volts - Too High??? Mercury 60hp OB

Mercury60 said:

Thanks guys! I really understand what the heck is going on now. Its good to know that I'm not up sh*ts creek due to the 16 volts. Its also good to know that the stator is acting normally.

The only electrical devices on this boat are a gps chartplotter/fishfinder and the running lights. Sooner or later there will be a stereo but thats down the road.

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If/when your gps chartplotter/fishfinder (and all other 12V accessories) fries due to a 16V input, you may rethink your comfort in allowing 16V to feed those components.