16v output from Johnson 112spl

G

gregBR549

Cadet
Joined
Jan 3, 2008
Messages
8
I have a Johnson 112 that is putting out up to 16 volts at WOT and about 13v at idle. From what I have read, this is normal and by design. It is unregulated from the factory. It only has a rectifier, not a regulator. Is that right?
My concern is overcharging the batteries and (more importantly) frying my electronics. My depth finder manual says operating voltage from 10-15v. I am considering using a 12v zener diode in parallel at my electronics to protect them. Is this a common fix? How about overcharging the batteries and getting fumes in my bilge. Should I be concerned about that?
thanks
Greg
 
J

John_S

Rear Admiral
Joined
Jun 21, 2004
Messages
4,269
Re: 16v output from Johnson 112spl

I have an unregulated outboard, and when the battery is fully charged it can climb to 16V while underway. I turn on some lights, airaiters, live-well pumps, etc to keep the voltage down.
 
bruceb58

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,476
Re: 16v output from Johnson 112spl

You can use a zener but you have to put in a resistor in series to limit the current through the zener. Note that you will have a voltage drop across the resistor as well so take that into consideration and it will be drawing power at all times, even when the device is turned off. You would be better off just using the resistor to drop the voltage or just 2 or 3 power diodes in series.
 
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